diff --git a/CHANGELOG.md b/CHANGELOG.md
index 87e0259..07cf15c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,30 @@ each tagged release (`v<version>`) is archived on Zenodo with its own DOI (see
 [Releasing](#releasing)). Plans and acceptance criteria for each round are in
 `PLAN_ROUND_<n>.md`.
 
+## 0.15.1 (patch): B01003 total from B01001 for firewall-blocked VRE files
+
+- **`fetch_vre` substitute for the total-population VRE file.** census.gov's firewall
+  rejects the 2015-2019 Michigan tract B01003 file for every client (support ID
+  13979921158196382640). When a B01003 file is rejected or returns HTTP 404, `fetch_vre`
+  now reads line 1 ("Total:") of the B01001 file for the same release, geography and
+  state, and relabels it as B01003_001.
+  - Only this pair is substituted (`VRE_TOTAL_FALLBACKS`). On the 2015-2019 New York
+    tract files the two lines are identical in every cell. A live test
+    (`CENSUS_LIVE_TESTS=1`) re-checks this.
+  - The substitution is never silent. It issues a warning and is recorded in
+    `attrs["substitution"]`: requested URL, reason, the B01001 URL and its SHA-256, and
+    the verification. Manifest replicate records and methods text carry it.
+  - Other B01003 lines, other tables or failures, `allow_substitute=False`, or an
+    unavailable B01001 file still raise the original error. A new `lines=` argument
+    keeps only the requested table lines.
+- **Michigan 2015-2019 population covariance completed**
+  (`docs/audits/acs_sampling_covariance.md`), using the B01001 substitute. Results match
+  2020-2024 and New York, so the conclusions are unchanged.
+  - Order 1 within county is -0.075 [-0.103, -0.046] (2020-2024: -0.081).
+  - Across county it is -0.005 [-0.014, 0.004].
+  - The county aggregation ratio is 0.000.
+  - Split-half pair reliability is 0.64.
+
 ## 0.15.0 (Round 16): spatial methods validated under ACS sampling error
 
 - Project renamed **Census Research Engine** (github.com/cafeTechne/Census-Research-Engine);
diff --git a/CITATION.cff b/CITATION.cff
index 1088182..d9f72dd 100644
--- a/CITATION.cff
+++ b/CITATION.cff
@@ -12,7 +12,7 @@ authors:
   - alias: cafeTechne
 license: AGPL-3.0-or-later
 repository-code: "https://github.com/cafeTechne/Census-Research-Engine"
-version: "0.15.0"
+version: "0.15.1"
 doi: "10.5281/zenodo.23925301"
 # doi: Zenodo concept DOI, added after the first archived release (see CHANGELOG.md "Releasing").
 date-released: "2026-11-09"
diff --git a/README.md b/README.md
index 9111b2b..d8fbae6 100644
--- a/README.md
+++ b/README.md
@@ -51,7 +51,7 @@ Alternatively, set `BLS_USER_AGENT` to an identifying User-Agent that includes a
 | `CENSUS_PRICE_PARITY_DIR` | Alternate Regional Price Parity directory (default `data/price_parities/`); same treatment |
 | `BLS_USER_AGENT` | Identifying User-Agent for `scripts/update_price_indexes.py` |
 | `CENSUS_VRE_DIR` | Cache for downloaded Census Variance Replicate Estimate files (default `.cache/vre/`) |
-| `CENSUS_WWW2_MIN_INTERVAL` / `CENSUS_WWW2_ATTEMPTS` / `CENSUS_WWW2_BACKOFF_BASE` / `CENSUS_WWW2_REJECTED_RETRY_DELAY` | census.gov file downloads (`census/http.py`): seconds between requests to one host (default 1), attempts on HTTP 429/5xx or connection errors (4), backoff base in seconds (2; doubled per retry, capped at 60, honours `Retry-After`), and the wait before the single retry of a firewall "Request Rejected" page (30). A rejection that persists names the cache path where a browser-downloaded copy of the file is picked up |
+| `CENSUS_WWW2_MIN_INTERVAL` / `CENSUS_WWW2_ATTEMPTS` / `CENSUS_WWW2_BACKOFF_BASE` / `CENSUS_WWW2_REJECTED_RETRY_DELAY` | census.gov file downloads (`census/http.py`): seconds between requests to one host (default 1), attempts on HTTP 429/5xx or connection errors (4), backoff base in seconds (2; doubled per retry, capped at 60, honours `Retry-After`), and the wait before the single retry of a firewall "Request Rejected" page (30). A rejection that persists names the cache path where a browser-downloaded copy of the file is picked up; for a rejected (or 404) B01003 VRE file, `fetch_vre` instead reads the identical B01001 line 1 and records the substitution (`attrs["substitution"]`, with a warning) |
 | `CENSUS_LIVE_TESTS=1` | Enable live API contract tests and the live validation battery |
 
 ## Quick start
diff --git a/census/__init__.py b/census/__init__.py
index 760bf59..81e2dcd 100644
--- a/census/__init__.py
+++ b/census/__init__.py
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
 """Headless Census ACS data client and processing library."""
 
-__version__ = "0.15.0"
+__version__ = "0.15.1"
 
 from census.api import (
     DATASETS,
diff --git a/census/manifest.py b/census/manifest.py
index 5c9a6d7..3c8ab37 100644
--- a/census/manifest.py
+++ b/census/manifest.py
@@ -1587,6 +1587,8 @@ def _census_vre_replicates(m: Mapping[str, Any], frame: pd.DataFrame, codes_by_y
                 files.append({"table": table, "release": year, "summary_level": f.attrs.get("summary_level"),
                               "state_code": f.attrs.get("state_code"), "url": f.attrs.get("source_url"),
                               "sha256": f.attrs.get("sha256"), "moe_check": f.attrs.get("moe_check")})
+                if f.attrs.get("substitution"):  # B01003 total read from B01001 (census.replicate.fetch_vre)
+                    files[-1]["substitution"] = f.attrs["substitution"]
                 frames.append(f[f["GEOID"].astype(str).isin(want)])
             rows = pd.concat(frames, ignore_index=True) if frames else pd.DataFrame()
             for n in names:
@@ -2005,6 +2007,11 @@ def methods_section(manifest: Mapping[str, Any], results: Optional[Mapping[str,
                       "SHA-256 of each file in run.json"
                       + (f"; canonical SHA-256 of the replicates used `{rep_info['sha256']}`" if rep_info.get("sha256")
                          else "") + ")")
+        subs = [f["substitution"] for f in files if f.get("substitution")]
+        if subs:
+            rep_source += "; " + "; ".join(
+                f"{', '.join(s['lines'])} read from {', '.join(s['lines'].values())} of `{s['source_url']}` because "
+                f"`{s['requested_url']}` was unavailable ({s['reason']}); {s['verification']}" for s in subs)
         rep_short = " and replicate-based standard errors from Census VRE files"
     elif results is None and census_vre_source(m):
         rep_source = "the 80 replicate estimates of the Census VRE files fetched for the manifest's tables"
diff --git a/census/pipeline.py b/census/pipeline.py
index a01f4ea..9cd764f 100644
--- a/census/pipeline.py
+++ b/census/pipeline.py
@@ -103,7 +103,7 @@
 from census.stats import add_reliability_columns, clean_census_sentinels, parse_variable_code
 from census.tables import load_variable_metadata
 
-PACKAGE_VERSION = "0.15.0"
+PACKAGE_VERSION = "0.15.1"
 
 CONCORDANCE_MODES = ("fail", "strict", "code")
 MAX_ISSUES_IN_RESULT = 100
diff --git a/census/replicate.py b/census/replicate.py
index 3598c31..f0c77c3 100644
--- a/census/replicate.py
+++ b/census/replicate.py
@@ -685,7 +685,9 @@ def _download(
     raw = resp.content or b""
     content_type = str(resp.headers.get("Content-Type", ""))
     if resp.status_code == 404:
-        raise VREDownloadError(f"Not published (HTTP 404): {url}")
+        exc = VREDownloadError(f"Not published (HTTP 404): {url}")
+        exc.url, exc.status_code = url, 404  # type: ignore[attr-defined]
+        raise exc
     if resp.status_code != 200:
         raise VREDownloadError(f"HTTP {resp.status_code} for {url}")
     return raw, content_type
@@ -915,6 +917,54 @@ def num(col: str) -> np.ndarray:
     return out.reset_index(drop=True)
 
 
+# Substitute files for VRE files census.gov does not serve. Only the verified
+# pair is listed: B01003 (Total Population) line 1 and B01001 (Sex by Age)
+# line 1 ("Total:") are the same total population. Verified on 2026-11-09 for
+# the 2015-2019 New York tract files (B01003_36 and B01001_36, 4,918 tracts):
+# ESTIMATE, MOE and Var_Rep1-80 identical, 0 differing cells; the live test in
+# tests/test_replicate_live.py re-checks it. Needed because www2.census.gov's
+# firewall rejects .../2019/data/5-year/140/B01003_26.csv.zip for every client
+# (support ID 13979921158196382640) while B01001_26 downloads normally.
+VRE_TOTAL_FALLBACKS: Dict[Tuple[str, int], Tuple[str, int]] = {("B01003", 1): ("B01001", 1)}
+VRE_TOTAL_FALLBACK_TITLES: Dict[Tuple[str, int], str] = {("B01003", 1): "Total"}
+VRE_TOTAL_FALLBACK_VERIFICATION = (
+    "B01003 line 1 (Total population) equals B01001 line 1 (Total:) cell for cell: verified 2026-11-09 on the "
+    "2015-2019 New York tract VRE files (4,918 tracts; ESTIMATE, MOE and Var_Rep1-80 identical, 0 differing "
+    "cells); re-checked by tests/test_replicate_live.py (CENSUS_LIVE_TESTS=1)."
+)
+
+
+def _fallback_reason(exc: BaseException) -> Optional[str]:
+    """Why a download failed when the failure allows a substitute file (firewall rejection or HTTP 404); else None."""
+    if getattr(exc, "rejected", False):
+        sid = getattr(exc, "support_id", "") or "none shown"
+        return f"census.gov firewall 'Request Rejected' page (support ID {sid})"
+    if getattr(exc, "status_code", None) == 404:
+        return "HTTP 404 (not published)"
+    return None
+
+
+def _load_vre_file(
+    table: str,
+    year: int,
+    sumlev: str,
+    state: Optional[str],
+    session: Any,
+    cache_dir: Optional[str],
+    refresh: bool,
+) -> Tuple[bytes, Dict[str, Any], str, str]:
+    """(raw bytes, sidecar metadata, URL, cache path) of one VRE file, from the cache or downloaded."""
+    url = vre_url(table, year, sumlev, state)
+    path = os.path.join(cache_dir or vre_cache_dir(year), sumlev, url.rsplit("/", 1)[-1])
+    raw = None if refresh else _read_cached(path, url, _decompress)
+    if raw is None:
+        raw, ctype = _download(url, session=session, cache_path=path)
+        _decompress(raw)  # validate before caching
+        return raw, _write_cached(path, raw, url, ctype), url, path
+    with open(_sidecar_path(path), encoding="utf-8") as f:
+        return raw, json.load(f), url, path
+
+
 def fetch_vre(
     table: str,
     year: int,
@@ -925,12 +975,15 @@ def fetch_vre(
     cache_dir: Optional[str] = None,
     refresh: bool = False,
     check_moe: bool = True,
+    lines: Optional[Sequence[int]] = None,
+    allow_substitute: bool = True,
 ) -> pd.DataFrame:
     """Download (or read from cache) one VRE file and return its replicate frame.
 
     Tract and block-group files are per state, so ``state_code`` is required for
     them; for state-nested national files (state, county, county subdivision,
-    place, congressional district) ``state_code`` filters the rows.
+    place, congressional district) ``state_code`` filters the rows. ``lines``
+    (ORDER numbers) keeps only those table lines.
 
     Files are cached under ``$CENSUS_VRE_DIR`` (default ``.cache/vre``) as
     ``<year>/<sumlev>/<file>`` with a ``.json`` sidecar holding the source URL
@@ -938,6 +991,18 @@ def fetch_vre(
     ``client`` (a census.api client) is accepted for interface symmetry; only
     its ``session`` attribute is used, if present.
 
+    Substitute file (``VRE_TOTAL_FALLBACKS``): when the B01003 file cannot be
+    fetched because census.gov rejects it (firewall page) or answers HTTP 404,
+    and only line 1 is needed, the B01001 file of the same release, geography
+    and state is fetched and its line 1 ("Total:", verified identical cell for
+    cell) is returned relabelled as B01003_001 with title "Total". This is never
+    silent: a warning is issued, ``attrs["substitution"]`` records the
+    requested and the substituted file (URLs, SHA-256 of the file read, reason,
+    verification statement) and ``attrs["notes"]`` says so; ``source_url`` and
+    ``sha256`` name the file actually read. Other lines, other tables, other
+    failures, or ``allow_substitute=False`` raise the original error, as does
+    an unavailable substitute.
+
     With ``check_moe`` the published-MOE self-check runs on load and a warning
     is issued when any uncontrolled row disagrees beyond rounding.
     """
@@ -949,20 +1014,55 @@ def fetch_vre(
     state = str(state_code).zfill(2) if state_code not in (None, "") else None
     if state is not None and sumlev not in STATE_NESTED_SUMLEVS:
         raise ValueError(f"Summary level {sumlev} is not nested in states; omit state_code.")
-    url = vre_url(table, year, sumlev, state)
-    path = os.path.join(cache_dir or vre_cache_dir(year), sumlev, url.rsplit("/", 1)[-1])
-    raw = None if refresh else _read_cached(path, url, _decompress)
-    meta: Dict[str, Any]
-    if raw is None:
-        if session is None and client is not None:
-            session = getattr(client, "session", None)
-        raw, ctype = _download(url, session=session, cache_path=path)
-        _decompress(raw)  # validate before caching
-        meta = _write_cached(path, raw, url, ctype)
-    else:
-        with open(_sidecar_path(path), encoding="utf-8") as f:
-            meta = json.load(f)
+    wanted = None if lines is None else sorted({int(x) for x in lines})
+    if session is None and client is not None:
+        session = getattr(client, "session", None)
+    substitution: Optional[Dict[str, Any]] = None
+    try:
+        raw, meta, url, path = _load_vre_file(table, year, sumlev, state, session, cache_dir, refresh)
+    except VREDownloadError as exc:
+        reason = _fallback_reason(exc)
+        sub_lines = sorted(o for (t, o) in VRE_TOTAL_FALLBACKS if t == table)
+        if not allow_substitute or reason is None or not sub_lines:
+            raise
+        need = wanted if wanted is not None else sub_lines
+        other = [o for o in need if o not in sub_lines]
+        if other or not need:
+            raise VREDownloadError(
+                f"{exc}\nNo verified substitute file exists for {table} line(s) {other or need} (substitutes "
+                f"exist only for {[f'{table}_{o:03d}' for o in sub_lines]})."
+            ) from exc
+        src_table = VRE_TOTAL_FALLBACKS[(table, need[0])][0]
+        try:
+            raw, meta, url, path = _load_vre_file(src_table, year, sumlev, state, session, cache_dir, refresh)
+        except VREDownloadError:
+            raise exc from None  # the substitute is unavailable too: report the original failure
+        substitution = {
+            "requested_table": table,
+            "requested_url": getattr(exc, "url", None) or vre_url(table, year, sumlev, state),
+            "reason": reason,
+            "support_id": getattr(exc, "support_id", None),
+            "http_status": getattr(exc, "status_code", None),
+            "source_table": src_table,
+            "lines": {f"{table}_{o:03d}": "{}_{:03d}".format(*VRE_TOTAL_FALLBACKS[(table, o)]) for o in need},
+            "source_url": url,
+            "source_sha256": meta.get("sha256"),
+            "verification": VRE_TOTAL_FALLBACK_VERIFICATION,
+        }
+        wanted = need
     frame = read_vre_csv(raw)
+    if substitution is not None:
+        parts = []
+        for target, source in substitution["lines"].items():
+            part = frame[frame["variable"] == source].copy()
+            part["variable"] = target
+            part["title"] = VRE_TOTAL_FALLBACK_TITLES[(table, int(target.rsplit("_", 1)[1]))]
+            parts.append(part)
+        attrs = dict(frame.attrs)
+        frame = pd.concat(parts, ignore_index=True)
+        frame.attrs.update(attrs)
+    elif wanted is not None:
+        frame = frame[frame["variable"].isin({f"{table}_{o:03d}" for o in wanted})].reset_index(drop=True)
     if state is not None and sumlev not in PER_STATE_SUMLEVS:
         frame = frame[frame["GEOID"].str.startswith(state)].reset_index(drop=True)
     frame.attrs.update(
@@ -976,6 +1076,15 @@ def fetch_vre(
         cache_path=path,
         acquisition=meta.get("source", "download"),
     )
+    if substitution is not None:
+        note = (
+            f"{substitution['requested_url']} is unavailable ({substitution['reason']}); "
+            + ", ".join(f"{k} is {v}" for k, v in substitution["lines"].items())
+            + f" of {url} (SHA-256 {substitution['source_sha256']}), relabelled. {VRE_TOTAL_FALLBACK_VERIFICATION}"
+        )
+        frame.attrs["substitution"] = substitution
+        frame.attrs["notes"] = [f"substituted_source: {note}"]
+        warnings.warn(f"VRE substitute file used: {note}", stacklevel=2)
     if check_moe:
         report = verify_published_moe(frame)
         frame.attrs["moe_check"] = {k: v for k, v in report.items() if k != "mismatches"}
diff --git a/docs/audits/acs_sampling_covariance.md b/docs/audits/acs_sampling_covariance.md
index e371317..66f57f9 100644
--- a/docs/audits/acs_sampling_covariance.md
+++ b/docs/audits/acs_sampling_covariance.md
@@ -1,6 +1,6 @@
 # ACS sampling-error covariance between areas (VRE replicates)
 
-Generated 2026-11-09 06:54 UTC by `scripts/acs_error_covariance.py` (commit v0.14.0-29-g1847007-dirty, 10.0 min). PLAN_ROUND_16 workstream C (C1-C2). Status: **info** (gates nothing). Per-class numbers: `docs/audits/acs_sampling_covariance.csv` (written by the script; git-ignored like the other audit CSVs).
+Generated 2026-11-09 15:28 UTC by `scripts/acs_error_covariance.py` (commit v0.15.0-1-g981e832-dirty, 9.2 min). PLAN_ROUND_16 workstream C (C1-C2). Status: **info** (gates nothing). Per-class numbers: `docs/audits/acs_sampling_covariance.csv` (written by the script; git-ignored like the other audit CSVs).
 
 ## Question
 
@@ -38,6 +38,7 @@ Releases 2020-2024, 2015-2019; states Michigan (26) and New York (36). Files (ca
 | VRE | 2024 | county | `B17001.csv.zip` | `3d24fa18e9f005b3c9455d3bda4a4ab843eb8f443d423b56b00496b58ad0c605` |
 | VRE | 2024 | county | `B19001.csv.zip` | `95cb48eabcaef5c44fc68377f8b596f31cbb079d846bbea9c6bf7e83ba896d0f` |
 | boundary | 2024 | county | `cb_2024_us_county_500k.zip` | `da4051717caec55c75e3748c3608c2a3dbde8d1ff401bbaf4f952e3c3fb63ef1` |
+| VRE | 2019 | tract | `B01001_26.csv.zip` (substitute for `B01003_26.csv.zip`) | `4ef59dbb65e02ce8de6779cd40d382f3e143a17079b1ffa56dd886f60d72970a` |
 | VRE | 2019 | tract | `B25003_26.csv.zip` | `0b6a3f85d252700385d92a435396f24750d659b89f114e3d6006e525231317d4` |
 | VRE | 2019 | tract | `B17001_26.csv.zip` | `8f6e7fb8d21f80e605d03ce4fab11fc3a372184cb1e550d64b84cf779569d729` |
 | VRE | 2019 | tract | `B19001_26.csv.zip` | `0cd0858b255228c403627e3bd08094950a56e3d15d414446fd77a719ecf99168` |
@@ -53,15 +54,15 @@ Releases 2020-2024, 2015-2019; states Michigan (26) and New York (36). Files (ca
 | VRE | 2019 | county | `B19001.csv.zip` | `56374faae955dd44c9eec5f45c7b2d145781b6271028d714eae6ebafc2f260d3` |
 | boundary | 2019 | county | `cb_2019_us_county_500k.zip` | `1c4b703cd34c3f5e5e6368f91f1bd80de9281ef81ad91e005844848df9976c4b` |
 
-**Unavailable files** (skipped; the variables that need them are not analysed for that state and release, everything else is):
+**Substituted files** (census.replicate.fetch_vre, `VRE_TOTAL_FALLBACKS`):
 
-| year | level | state | table | URL | reason |
+| year | level | state | requested | reason | used instead |
 | :--- | :--- | :--- | :--- | :--- | :--- |
-| 2019 | tract | Michigan | B01003 | https://www2.census.gov/programs-surveys/acs/replicate_estimates/2019/data/5-year/140/B01003_26.csv.zip | census.gov firewall 'Request Rejected' page (support ID 13979921158196382640), also on the single delayed retry |
+| 2019 | tract | Michigan | https://www2.census.gov/programs-surveys/acs/replicate_estimates/2019/data/5-year/140/B01003_26.csv.zip | census.gov firewall 'Request Rejected' page (support ID 13979921158196382640) | B01003_001 = B01001_001 of https://www2.census.gov/programs-surveys/acs/replicate_estimates/2019/data/5-year/140/B01001_26.csv.zip |
 
-A rejection of one specific URL can persist while every other file in the same directory downloads normally, so it is not retried further. To include such a file, download it in a browser and save it as `$CENSUS_VRE_DIR/2019/140/B01003_26.csv.zip` (default `$CENSUS_VRE_DIR` = `.cache/vre`); census.replicate then records its SHA-256 with source 'manual download' and the report marks it.
+Basis: B01003 line 1 (Total population) equals B01001 line 1 (Total:) cell for cell: verified 2026-11-09 on the 2015-2019 New York tract VRE files (4,918 tracts; ESTIMATE, MOE and Var_Rep1-80 identical, 0 differing cells); re-checked by tests/test_replicate_live.py (CENSUS_LIVE_TESTS=1). The substitute file's SHA-256 is the one listed above.
 
-Versions: census-acs-toolkit 0.14.0, python 3.14.4, numpy 2.5.4, scipy 1.18.1, pandas 3.1.1, geopandas 1.2.0, libpysal 4.15.1
+Versions: census-acs-toolkit 0.15.1, python 3.14.4, numpy 2.5.4, scipy 1.18.1, pandas 3.1.1, geopandas 1.2.0, libpysal 4.15.1
 
 Areas analysed (after exclusions):
 
@@ -89,6 +90,7 @@ Areas analysed (after exclusions):
 | 2024 | New York | county | poverty_rate | proportion | 62 | 62 | 0 |  |
 | 2024 | New York | county | owner_share | proportion | 62 | 62 | 0 |  |
 | 2024 | New York | county | median_hh_income | median | 62 | 62 | 0 | 0 top/bottom-coded medians excluded |
+| 2019 | Michigan | tract | population | count | 2772 | 2754 | 18 |  |
 | 2019 | Michigan | tract | households | count | 2772 | 2738 | 34 |  |
 | 2019 | Michigan | tract | poverty_count | count | 2772 | 2736 | 36 |  |
 | 2019 | Michigan | tract | poverty_rate | proportion | 2772 | 2734 | 8 |  |
@@ -111,7 +113,7 @@ Areas analysed (after exclusions):
 | 2019 | New York | county | owner_share | proportion | 62 | 62 | 0 |  |
 | 2019 | New York | county | median_hh_income | median | 62 | 62 | 0 | 0 top/bottom-coded medians excluded |
 
-Skipped: 2024 Michigan county population: 83 controlled (no sampling error); 2024 New York county population: 62 controlled (no sampling error); 2019 Michigan tract population: VRE file B01003 unavailable (see Data: unavailable files); 2019 Michigan county population: 83 controlled (no sampling error); 2019 New York county population: 62 controlled (no sampling error).
+Skipped: 2024 Michigan county population: 83 controlled (no sampling error); 2024 New York county population: 62 controlled (no sampling error); 2019 Michigan county population: 83 controlled (no sampling error); 2019 New York county population: 62 controlled (no sampling error).
 
 ## Results 2020-2024
 
@@ -542,6 +544,7 @@ Mean pairwise r [95% interval] (number of pairs) by queen contiguity order.
 
 | state | variable | order 1 | order 2 | order 3 | beyond order 3 |
 | :--- | :--- | :--- | :--- | :--- | :--- |
+| Michigan | population | -0.066 [-0.088, -0.044] (n=8661) | -0.014 [-0.017, -0.011] (n=20170) | -0.004 [-0.005, -0.003] (n=34283) | -0.000 [-0.001, -0.000] (n=235969) |
 | Michigan | households | 0.025 [0.016, 0.033] (n=8614) | 0.006 [0.000, 0.013] (n=20000) | 0.001 [-0.002, 0.005] (n=33974) | -0.000 [-0.001, 0.001] (n=234537) |
 | Michigan | poverty_count | -0.004 [-0.007, -0.001] (n=8601) | -0.002 [-0.004, 0.000] (n=19957) | 0.000 [-0.002, 0.002] (n=33911) | -0.000 [-0.000, 0.000] (n=234178) |
 | Michigan | poverty_rate | -0.000 [-0.003, 0.003] (n=8581) | -0.001 [-0.003, 0.001] (n=19916) | 0.000 [-0.002, 0.002] (n=33847) | 0.000 [-0.001, 0.001] (n=233863) |
@@ -573,6 +576,7 @@ Mean pairwise r [95% interval] (number of pairs) by queen contiguity order.
 
 | state | variable | order 1 / within county | order 1 / across county | order 2 / within county | order 2 / across county | beyond order 3 / within county | beyond order 3 / across county |
 | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- |
+| Michigan | population | -0.075 [-0.103, -0.046] (n=7608) | -0.005 [-0.014, 0.004] (n=1053) | -0.019 [-0.026, -0.013] (n=14988) | 0.001 [-0.003, 0.005] (n=5182) | -0.001 [-0.001, 0.000] (n=146947) | -0.000 [-0.001, 0.001] (n=89022) |
 | Michigan | households | 0.028 [0.020, 0.035] (n=7563) | 0.001 [-0.012, 0.014] (n=1051) | 0.008 [0.001, 0.016] (n=14828) | 0.001 [-0.003, 0.005] (n=5172) | -0.001 [-0.003, 0.002] (n=146625) | 0.000 [-0.001, 0.001] (n=87912) |
 | Michigan | poverty_count | -0.005 [-0.008, -0.002] (n=7549) | 0.001 [-0.007, 0.010] (n=1052) | -0.001 [-0.003, 0.001] (n=14793) | -0.003 [-0.008, 0.001] (n=5164) | 0.000 [-0.000, 0.001] (n=146388) | -0.001 [-0.002, 0.000] (n=87790) |
 | Michigan | poverty_rate | -0.000 [-0.003, 0.002] (n=7531) | 0.001 [-0.007, 0.009] (n=1050) | 0.000 [-0.002, 0.003] (n=14758) | -0.003 [-0.007, 0.002] (n=5158) | 0.001 [0.000, 0.001] (n=146203) | -0.001 [-0.002, 0.000] (n=87660) |
@@ -591,6 +595,7 @@ Tracts:
 
 | state | variable | order 1 rook (shared edge) | order 1 queen-only (corner) |
 | :--- | :--- | :--- | :--- |
+| Michigan | population | -0.075 [-0.099, -0.051] (n=7076) | -0.028 [-0.035, -0.020] (n=1585) |
 | Michigan | households | 0.025 [0.017, 0.034] (n=7033) | 0.021 [0.009, 0.033] (n=1581) |
 | Michigan | poverty_count | -0.005 [-0.008, -0.001] (n=7018) | -0.002 [-0.008, 0.004] (n=1583) |
 | Michigan | poverty_rate | -0.000 [-0.003, 0.003] (n=7001) | 0.001 [-0.006, 0.007] (n=1580) |
@@ -624,6 +629,7 @@ Tracts:
 
 | state | variable | 0-2 km | 2-5 km | 5-10 km | 10-20 km | 20-50 km | 50-100 km | 100-inf km |
 | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- |
+| Michigan | population | -0.039 [-0.078, 0.001] (n=3830) | -0.021 [-0.050, 0.008] (n=19110) | -0.008 [-0.019, 0.003] (n=35824) | -0.002 [-0.005, 0.001] (n=69777) | -0.001 [-0.004, 0.002] (n=91586) | -0.000 [-0.003, 0.002] (n=20557) | -0.000 [-0.001, 0.001] (n=58399) |
 | Michigan | households | 0.032 [0.006, 0.058] (n=3786) | 0.014 [0.005, 0.023] (n=18947) | 0.003 [0.001, 0.006] (n=35548) | -0.002 [-0.005, 0.002] (n=69531) | -0.001 [-0.003, 0.000] (n=91378) | -0.001 [-0.004, 0.002] (n=20313) | 0.001 [-0.001, 0.002] (n=57622) |
 | Michigan | poverty_count | -0.003 [-0.010, 0.004] (n=3789) | -0.002 [-0.005, 0.001] (n=18945) | -0.001 [-0.002, -0.000] (n=35516) | 0.000 [-0.001, 0.001] (n=69418) | 0.000 [-0.000, 0.001] (n=91157) | -0.000 [-0.003, 0.002] (n=20216) | -0.000 [-0.002, 0.001] (n=57606) |
 | Michigan | poverty_rate | 0.001 [-0.006, 0.008] (n=3778) | -0.001 [-0.002, 0.001] (n=18895) | -0.001 [-0.002, 0.000] (n=35416) | 0.001 [-0.000, 0.001] (n=69298) | 0.000 [-0.000, 0.001] (n=91079) | -0.001 [-0.003, 0.002] (n=20196) | -0.000 [-0.002, 0.001] (n=57545) |
@@ -655,6 +661,7 @@ Counties:
 
 | state | variable | counties | tracts | pooled ratio (SE) | median county ratio | implied mean within-county r (SE) |
 | :--- | :--- | :--- | :--- | :--- | :--- | :--- |
+| Michigan | population | 83 | 2754 | 0.000 (0.000) | 0.000 | -0.0046 (0.0000) |
 | Michigan | households | 82 | 2737 | 0.902 (0.053) | 0.798 | -0.0006 (0.0003) |
 | Michigan | poverty_count | 83 | 2736 | 0.886 (0.043) | 0.939 | -0.0006 (0.0002) |
 | New York | population | 62 | 4854 | 0.000 (0.000) | 0.000 | -0.0032 (0.0000) |
@@ -669,11 +676,12 @@ Michigan x New York pairs (independent samples):
 
 | geography | variable | pairs | mean r (SE) | SD of r | 95% |r| | share |r| > analytic critical |
 | :--- | :--- | :--- | :--- | :--- | :--- | :--- |
-| tract | households | 50000 | 0.0003 (0.0005) | 0.116 | 0.229 | 0.060 |
-| tract | poverty_count | 50000 | -0.0005 (0.0004) | 0.115 | 0.231 | 0.062 |
-| tract | poverty_rate | 50000 | -0.0007 (0.0004) | 0.116 | 0.234 | 0.063 |
-| tract | owner_share | 50000 | -0.0002 (0.0004) | 0.115 | 0.226 | 0.058 |
-| tract | median_hh_income | 50000 | 0.0014 (0.0005) | 0.116 | 0.227 | 0.059 |
+| tract | population | 50000 | -0.0006 (0.0006) | 0.115 | 0.224 | 0.056 |
+| tract | households | 50000 | 0.0000 (0.0004) | 0.116 | 0.228 | 0.060 |
+| tract | poverty_count | 50000 | 0.0000 (0.0004) | 0.116 | 0.234 | 0.064 |
+| tract | poverty_rate | 50000 | -0.0001 (0.0005) | 0.116 | 0.232 | 0.063 |
+| tract | owner_share | 50000 | 0.0001 (0.0005) | 0.115 | 0.224 | 0.056 |
+| tract | median_hh_income | 50000 | 0.0004 (0.0004) | 0.115 | 0.223 | 0.056 |
 | county | households | 5146 | 0.0285 (0.0028) | 0.120 | 0.240 | 0.078 |
 | county | poverty_count | 5146 | 0.0055 (0.0020) | 0.116 | 0.228 | 0.061 |
 | county | poverty_rate | 5146 | 0.0055 (0.0020) | 0.116 | 0.229 | 0.063 |
@@ -684,6 +692,7 @@ Derangement null on far pairs (same state, beyond order 3):
 
 | state | geography | variable | pairs | mean | SD | 95% |r| |
 | :--- | :--- | :--- | :--- | :--- | :--- | :--- |
+| Michigan | tract | population | 235969 | 0.0000 | 0.112 | 0.219 |
 | Michigan | tract | households | 234537 | 0.0004 | 0.113 | 0.222 |
 | Michigan | tract | poverty_count | 234178 | 0.0002 | 0.112 | 0.219 |
 | Michigan | tract | poverty_rate | 233863 | 0.0003 | 0.112 | 0.219 |
@@ -710,6 +719,7 @@ Replicate design spectrum (lowest eigenvalues relative to the mean; Marchenko-Pa
 
 | state | geography | variable | lowest 4 eigenvalues (MP edge) | near-null | effective replicates | null SD 1/sqrt(eff.) |
 | :--- | :--- | :--- | :--- | :--- | :--- | :--- |
+| Michigan | tract | population | 0.042 0.050 0.077 0.432 (0.688) | 3 | 77 | 0.114 |
 | Michigan | tract | households | 0.052 0.054 0.078 0.400 (0.687) | 3 | 77 | 0.114 |
 | Michigan | tract | poverty_count | 0.025 0.025 0.052 0.410 (0.687) | 3 | 77 | 0.114 |
 | Michigan | tract | poverty_rate | 0.026 0.026 0.054 0.409 (0.687) | 3 | 77 | 0.114 |
@@ -736,50 +746,54 @@ Spread of pairwise r per class: SD, excess SD over the analytic null (sqrt(SD^2
 
 | state | geography | variable | class | SD of r | excess SD (analytic) | excess SD (cross-state) | share |r| > crit |
 | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- |
+| Michigan | tract | population | order 1 | 0.185 | 0.148 | 0.145 | 0.163 |
+| Michigan | tract | population | order 2 | 0.126 | 0.059 | 0.053 | 0.076 |
+| Michigan | tract | population | order 3 | 0.119 | 0.040 | 0.031 | 0.063 |
+| Michigan | tract | population | beyond order 3 | 0.115 | 0.028 | 0.012 | 0.058 |
 | Michigan | tract | households | order 1 | 0.140 | 0.085 | 0.079 | 0.115 |
-| Michigan | tract | households | order 2 | 0.124 | 0.054 | 0.044 | 0.076 |
-| Michigan | tract | households | order 3 | 0.119 | 0.041 | 0.026 | 0.066 |
-| Michigan | tract | households | beyond order 3 | 0.117 | 0.034 | 0.011 | 0.061 |
+| Michigan | tract | households | order 2 | 0.124 | 0.054 | 0.043 | 0.076 |
+| Michigan | tract | households | order 3 | 0.119 | 0.041 | 0.025 | 0.066 |
+| Michigan | tract | households | beyond order 3 | 0.117 | 0.034 | 0.010 | 0.061 |
 | Michigan | tract | poverty_count | order 1 | 0.114 | 0.024 | 0.000 | 0.061 |
-| Michigan | tract | poverty_count | order 2 | 0.116 | 0.030 | 0.010 | 0.064 |
-| Michigan | tract | poverty_count | order 3 | 0.115 | 0.029 | 0.007 | 0.064 |
-| Michigan | tract | poverty_count | beyond order 3 | 0.116 | 0.031 | 0.013 | 0.064 |
+| Michigan | tract | poverty_count | order 2 | 0.116 | 0.030 | 0.000 | 0.064 |
+| Michigan | tract | poverty_count | order 3 | 0.115 | 0.029 | 0.000 | 0.064 |
+| Michigan | tract | poverty_count | beyond order 3 | 0.116 | 0.031 | 0.008 | 0.064 |
 | Michigan | tract | poverty_rate | order 1 | 0.114 | 0.023 | 0.000 | 0.060 |
 | Michigan | tract | poverty_rate | order 2 | 0.116 | 0.030 | 0.000 | 0.062 |
 | Michigan | tract | poverty_rate | order 3 | 0.116 | 0.030 | 0.000 | 0.062 |
-| Michigan | tract | poverty_rate | beyond order 3 | 0.116 | 0.030 | 0.005 | 0.063 |
-| Michigan | tract | owner_share | order 1 | 0.115 | 0.027 | 0.000 | 0.058 |
+| Michigan | tract | poverty_rate | beyond order 3 | 0.116 | 0.030 | 0.006 | 0.063 |
+| Michigan | tract | owner_share | order 1 | 0.115 | 0.027 | 0.010 | 0.058 |
 | Michigan | tract | owner_share | order 2 | 0.115 | 0.025 | 0.000 | 0.058 |
-| Michigan | tract | owner_share | order 3 | 0.115 | 0.028 | 0.006 | 0.059 |
-| Michigan | tract | owner_share | beyond order 3 | 0.115 | 0.029 | 0.009 | 0.059 |
+| Michigan | tract | owner_share | order 3 | 0.115 | 0.028 | 0.013 | 0.059 |
+| Michigan | tract | owner_share | beyond order 3 | 0.115 | 0.029 | 0.014 | 0.059 |
 | Michigan | tract | median_hh_income | order 1 | 0.113 | 0.019 | 0.000 | 0.055 |
-| Michigan | tract | median_hh_income | order 2 | 0.116 | 0.032 | 0.009 | 0.060 |
-| Michigan | tract | median_hh_income | order 3 | 0.116 | 0.029 | 0.000 | 0.058 |
-| Michigan | tract | median_hh_income | beyond order 3 | 0.115 | 0.027 | 0.000 | 0.057 |
-| New York | tract | population | order 1 | 0.173 | 0.133 | - | 0.122 |
-| New York | tract | population | order 3 | 0.118 | 0.038 | - | 0.060 |
-| New York | tract | population | order 2 | 0.124 | 0.053 | - | 0.069 |
-| New York | tract | population | beyond order 3 | 0.115 | 0.029 | - | 0.058 |
+| Michigan | tract | median_hh_income | order 2 | 0.116 | 0.032 | 0.019 | 0.060 |
+| Michigan | tract | median_hh_income | order 3 | 0.116 | 0.029 | 0.015 | 0.058 |
+| Michigan | tract | median_hh_income | beyond order 3 | 0.115 | 0.027 | 0.009 | 0.057 |
+| New York | tract | population | order 1 | 0.173 | 0.133 | 0.130 | 0.122 |
+| New York | tract | population | order 3 | 0.118 | 0.038 | 0.028 | 0.060 |
+| New York | tract | population | order 2 | 0.124 | 0.053 | 0.046 | 0.069 |
+| New York | tract | population | beyond order 3 | 0.115 | 0.029 | 0.013 | 0.058 |
 | New York | tract | households | order 1 | 0.131 | 0.067 | 0.059 | 0.090 |
-| New York | tract | households | order 3 | 0.118 | 0.038 | 0.021 | 0.065 |
-| New York | tract | households | order 2 | 0.120 | 0.044 | 0.030 | 0.069 |
-| New York | tract | households | beyond order 3 | 0.117 | 0.033 | 0.009 | 0.061 |
-| New York | tract | poverty_count | order 1 | 0.115 | 0.028 | 0.005 | 0.063 |
+| New York | tract | households | order 3 | 0.118 | 0.038 | 0.020 | 0.065 |
+| New York | tract | households | order 2 | 0.120 | 0.044 | 0.029 | 0.069 |
+| New York | tract | households | beyond order 3 | 0.117 | 0.033 | 0.006 | 0.061 |
+| New York | tract | poverty_count | order 1 | 0.115 | 0.028 | 0.000 | 0.063 |
 | New York | tract | poverty_count | order 3 | 0.115 | 0.027 | 0.000 | 0.062 |
-| New York | tract | poverty_count | order 2 | 0.116 | 0.029 | 0.008 | 0.064 |
-| New York | tract | poverty_count | beyond order 3 | 0.115 | 0.029 | 0.007 | 0.064 |
+| New York | tract | poverty_count | order 2 | 0.116 | 0.029 | 0.000 | 0.064 |
+| New York | tract | poverty_count | beyond order 3 | 0.115 | 0.029 | 0.000 | 0.064 |
 | New York | tract | poverty_rate | order 1 | 0.115 | 0.027 | 0.000 | 0.066 |
 | New York | tract | poverty_rate | order 3 | 0.115 | 0.027 | 0.000 | 0.062 |
 | New York | tract | poverty_rate | order 2 | 0.115 | 0.029 | 0.000 | 0.062 |
 | New York | tract | poverty_rate | beyond order 3 | 0.115 | 0.029 | 0.000 | 0.063 |
-| New York | tract | owner_share | order 1 | 0.115 | 0.025 | 0.000 | 0.059 |
-| New York | tract | owner_share | order 3 | 0.116 | 0.029 | 0.009 | 0.059 |
-| New York | tract | owner_share | order 2 | 0.115 | 0.028 | 0.003 | 0.059 |
-| New York | tract | owner_share | beyond order 3 | 0.115 | 0.029 | 0.008 | 0.059 |
-| New York | tract | median_hh_income | order 1 | 0.115 | 0.029 | 0.000 | 0.059 |
-| New York | tract | median_hh_income | order 3 | 0.115 | 0.028 | 0.000 | 0.057 |
-| New York | tract | median_hh_income | order 2 | 0.115 | 0.027 | 0.000 | 0.057 |
-| New York | tract | median_hh_income | beyond order 3 | 0.115 | 0.027 | 0.000 | 0.058 |
+| New York | tract | owner_share | order 1 | 0.115 | 0.025 | 0.003 | 0.059 |
+| New York | tract | owner_share | order 3 | 0.116 | 0.029 | 0.014 | 0.059 |
+| New York | tract | owner_share | order 2 | 0.115 | 0.028 | 0.012 | 0.059 |
+| New York | tract | owner_share | beyond order 3 | 0.115 | 0.029 | 0.014 | 0.059 |
+| New York | tract | median_hh_income | order 1 | 0.115 | 0.029 | 0.014 | 0.059 |
+| New York | tract | median_hh_income | order 3 | 0.115 | 0.028 | 0.011 | 0.057 |
+| New York | tract | median_hh_income | order 2 | 0.115 | 0.027 | 0.008 | 0.057 |
+| New York | tract | median_hh_income | beyond order 3 | 0.115 | 0.027 | 0.009 | 0.058 |
 | Michigan | county | households | order 1 | 0.124 | 0.054 | 0.032 | 0.096 |
 | Michigan | county | households | order 3 | 0.115 | 0.027 | 0.000 | 0.064 |
 | Michigan | county | households | order 2 | 0.117 | 0.033 | 0.000 | 0.062 |
@@ -827,6 +841,10 @@ Per class: half-A and half-B class means (random split), and the reliability of
 
 | state | geography | variable | class | pairs | mean (half A) | mean (half B) | reliability (random / odd-even / first-last) |
 | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- |
+| Michigan | tract | population | order 1 | 8661 | -0.067 | -0.064 | 0.64 / 0.65 / 0.64 |
+| Michigan | tract | population | order 2 | 20170 | -0.013 | -0.015 | 0.21 / 0.22 / 0.22 |
+| Michigan | tract | population | order 3 | 34283 | -0.005 | -0.004 | 0.12 / 0.11 / 0.10 |
+| Michigan | tract | population | beyond order 3 | 235969 | -0.001 | -0.000 | 0.06 / 0.06 / 0.03 |
 | Michigan | tract | households | order 1 | 8614 | 0.022 | 0.027 | 0.37 / 0.37 / 0.35 |
 | Michigan | tract | households | order 2 | 20000 | 0.005 | 0.007 | 0.19 / 0.19 / 0.20 |
 | Michigan | tract | households | order 3 | 33974 | 0.001 | 0.002 | 0.11 / 0.12 / 0.13 |
@@ -918,6 +936,18 @@ Mean r per class in each release (different tract vintages: 2010 tracts in 2015-
 
 | state | geography | variable | class | 2019 | 2024 | difference (SE) |
 | :--- | :--- | :--- | :--- | :--- | :--- | :--- |
+| Michigan | tract | population | order 1 | -0.066 [-0.088, -0.044] | -0.071 [-0.090, -0.052] | -0.004 (0.015) |
+| Michigan | tract | population | order 2 | -0.014 [-0.017, -0.011] | -0.014 [-0.017, -0.011] | 0.000 (0.002) |
+| Michigan | tract | population | order 3 | -0.004 [-0.005, -0.003] | -0.004 [-0.005, -0.003] | 0.000 (0.001) |
+| Michigan | tract | population | beyond order 3 | -0.000 [-0.001, -0.000] | -0.001 [-0.001, 0.000] | -0.000 (0.000) |
+| Michigan | tract | population | order 1 / within county | -0.075 [-0.103, -0.046] | -0.081 [-0.106, -0.056] | -0.006 (0.019) |
+| Michigan | tract | population | order 2 / within county | -0.019 [-0.026, -0.013] | -0.018 [-0.024, -0.012] | 0.001 (0.005) |
+| Michigan | tract | population | order 2 / across county | 0.001 [-0.003, 0.005] | -0.001 [-0.005, 0.002] | -0.002 (0.003) |
+| Michigan | tract | population | order 1 / across county | -0.005 [-0.014, 0.004] | 0.003 [-0.007, 0.014] | 0.008 (0.007) |
+| Michigan | tract | population | order 3 / across county | -0.000 [-0.003, 0.002] | 0.001 [-0.001, 0.003] | 0.001 (0.001) |
+| Michigan | tract | population | order 3 / within county | -0.007 [-0.009, -0.004] | -0.007 [-0.009, -0.006] | -0.001 (0.001) |
+| Michigan | tract | population | beyond order 3 / within county | -0.001 [-0.001, 0.000] | -0.001 [-0.001, -0.000] | -0.000 (0.000) |
+| Michigan | tract | population | beyond order 3 / across county | -0.000 [-0.001, 0.001] | 0.000 [-0.001, 0.001] | 0.000 (0.001) |
 | Michigan | tract | households | order 1 | 0.025 [0.016, 0.033] | -0.025 [-0.033, -0.017] | -0.050 (0.006) |
 | Michigan | tract | households | order 2 | 0.006 [0.000, 0.013] | -0.008 [-0.011, -0.004] | -0.014 (0.004) |
 | Michigan | tract | households | order 3 | 0.001 [-0.002, 0.005] | -0.003 [-0.005, -0.002] | -0.005 (0.002) |
@@ -1151,19 +1181,27 @@ stated). r is the replicate correlation of two areas' sampling errors.
    scored on held-out replicates after removing the design directions, it is worse than independence
    for every variable (-25 to -50 nats for tracts). Without that projection it appeared to gain 30-90
    nats, entirely from the cross-half dependence created by the near-null design directions.
-6. **Stability across releases (tracts and counties, 2015-2019 vs 2020-2024).** One 2015-2019 file is
-   missing: Michigan tract total population (`2019/data/5-year/140/B01003_26.csv.zip`). census.gov's
-   firewall answered that one URL with its 'Request Rejected' page (support ID 13979921158196382640) on
-   the first request and on the single delayed retry, while every other 2019 tract file, including New
-   York's B01003_36 from the same directory, downloaded normally; the rejection is URL-specific, not
-   rate limiting (see Data: unavailable files). So the 2015-2019 tract comparison has no Michigan
-   population row; everything else was analysed. Results: (a) **Uncontrolled variables are stable.**
+6. **Stability across releases (tracts and counties, 2015-2019 vs 2020-2024).** One 2015-2019 file,
+   Michigan tract total population (`2019/data/5-year/140/B01003_26.csv.zip`), is refused by census.gov's
+   firewall ('Request Rejected', support ID 13979921158196382640) for every client, while every other
+   2019 tract file, including New York's B01003_36 from the same directory, downloads normally. Its only
+   line is read instead from line 1 ("Total:") of the same release's Michigan tract B01001 file
+   (B01001_26; see Data: substituted files). The two lines are the same total population: in the New York
+   2015-2019 tract files B01003 line 1 and B01001 line 1 agree in ESTIMATE, MOE and all 80 replicates for
+   all 4,918 tracts (0 differing cells), a check re-run by tests/test_replicate_live.py. All variables are
+   therefore analysed in both states and releases. Results: (a) **Uncontrolled variables are stable.**
    Poverty count, poverty rate, owner share and median income stay at 0 to within +/-0.005 at every order
    in both states and releases; of 108 tract class comparisons for them, 3 differ by more than 2 combined
-   SEs (about 5 expected by chance; largest |z| 2.5, all differences <= 0.004). (b) **Population (New
-   York) is stable**: order 1 -0.039 [-0.060, -0.018] in 2015-2019 vs -0.040 [-0.060, -0.020] (within
-   county -0.042 vs -0.043), the same fast decay, a county aggregation ratio of 0.000 again (tract errors
-   sum to zero within a county), and split-half pair reliability 0.60 (2020-2024: 0.61). (c)
+   SEs (about 5 expected by chance; largest |z| 2.5, all differences <= 0.004). (b) **Population is stable
+   in both states.** New York: order 1 -0.039 [-0.060, -0.018] in 2015-2019 vs -0.040 [-0.060, -0.020]
+   (within county -0.042 vs -0.043), the same fast decay, a county aggregation ratio of 0.000 again (tract
+   errors sum to zero within a county), and split-half pair reliability 0.60 (2020-2024: 0.61). Michigan
+   (B01001 line 1): order 1 -0.066 [-0.088, -0.044] vs -0.071 [-0.090, -0.052]; within county -0.075
+   [-0.103, -0.046] vs -0.081 [-0.106, -0.056]; across county -0.005 [-0.014, 0.004] vs +0.003 [-0.007,
+   0.014]; order 2 within county -0.019 vs -0.018; rook vs corner-only -0.075 vs -0.028 (2020-2024: -0.080
+   vs -0.029); aggregation ratio 0.000 in both releases; split-half pair reliability at order 1 0.64
+   (2020-2024: 0.67). Every Michigan population class difference between releases is at most 0.008
+   (order 1 across county, 1.1 combined SEs). As in 2020-2024, Michigan's within-county order-1 correlation is nearly twice New York's. (c)
    **Households change sign.** Occupied housing units (B25003_001) in 2015-2019 have *positive* mean r
    between neighbouring tracts in the same county - Michigan order 1 +0.025 [0.016, 0.033] (within county
    +0.028), New York +0.012 [0.003, 0.020] - against -0.025 and -0.015 in 2020-2024 (differences 8.4 and
@@ -1209,8 +1247,8 @@ analyses map it is indistinguishable from zero.**
   stress tests outside the observed range, not plausible ACS conditions for these variables; the
   realistic end of the grid is -0.1..0.05. Correlated-error scenarios with large positive rho should be
   stated as hypothetical (for example for variables or survey designs not studied here).
-* Limits: two states, two releases at tract level (2015-2019 without Michigan population: firewall
-  rejection of that one file), 80 replicates (about 77 effective), and counties as a proxy for weighting
+* Limits: two states, two releases at tract level (2015-2019 Michigan population read from B01001 line
+  1, verified identical to B01003 line 1; Findings 6), 80 replicates (about 77 effective), and counties as a proxy for weighting
   areas. The 95% |r| of 0.23 for a single pair means no individual pair can be
   flagged; only class means are evidence.
 
diff --git a/scripts/acs_error_covariance.py b/scripts/acs_error_covariance.py
index 1f3815b..a6a4f72 100644
--- a/scripts/acs_error_covariance.py
+++ b/scripts/acs_error_covariance.py
@@ -118,6 +118,8 @@ def _load_tables(year, level, state, files):
         files.append({"kind": "VRE", "year": year, "level": level, "state": state, "table": t,
                       "url": f.attrs["source_url"], "sha256": f.attrs["sha256"],
                       "acquisition": f.attrs.get("acquisition", "download")})
+        if f.attrs.get("substitution"):  # e.g. B01003 total read from B01001 (census.replicate.fetch_vre)
+            files[-1]["substitution"] = f.attrs["substitution"]
         frames[t] = f
     return frames
 
@@ -519,8 +521,20 @@ def write_report(df, extras, files, years, elapsed, findings, conclusion):
         seen.add(f["url"])
         name = f"`{f['url'].rsplit('/', 1)[-1]}`" + (" (manual download)" if f.get("acquisition") == "manual download"
                                                      else "")
+        if f.get("substitution"):
+            name += f" (substitute for `{f['substitution']['requested_url'].rsplit('/', 1)[-1]}`)"
         rows.append([f["kind"], f["year"], f["level"], name, f"`{f['sha256']}`"])
     L.append(_md_table(["kind", "year", "level", "file", "SHA-256"], rows) + "\n")
+    subs = [f for f in files if f.get("substitution")]
+    if subs:
+        L.append("**Substituted files** (census.replicate.fetch_vre, `VRE_TOTAL_FALLBACKS`):\n")
+        L.append(_md_table(["year", "level", "state", "requested", "reason", "used instead"],
+                           [[f["year"], f["level"], STATES.get(f["state"], f["state"]),
+                             f["substitution"]["requested_url"], f["substitution"]["reason"],
+                             ", ".join(f"{k} = {v} of {f['substitution']['source_url']}"
+                                       for k, v in f["substitution"]["lines"].items())] for f in subs]) + "\n")
+        L.append("Basis: " + subs[0]["substitution"]["verification"] + " The substitute file's SHA-256 is the one "
+                 "listed above.\n")
     missing = [f for f in files if f.get("unavailable")]
     if missing:
         L.append("**Unavailable files** (skipped; the variables that need them are not analysed for that state "
@@ -816,19 +830,27 @@ def interpret(df, extras, years):
    scored on held-out replicates after removing the design directions, it is worse than independence
    for every variable (-25 to -50 nats for tracts). Without that projection it appeared to gain 30-90
    nats, entirely from the cross-half dependence created by the near-null design directions.
-6. **Stability across releases (tracts and counties, 2015-2019 vs 2020-2024).** One 2015-2019 file is
-   missing: Michigan tract total population (`2019/data/5-year/140/B01003_26.csv.zip`). census.gov's
-   firewall answered that one URL with its 'Request Rejected' page (support ID 13979921158196382640) on
-   the first request and on the single delayed retry, while every other 2019 tract file, including New
-   York's B01003_36 from the same directory, downloaded normally; the rejection is URL-specific, not
-   rate limiting (see Data: unavailable files). So the 2015-2019 tract comparison has no Michigan
-   population row; everything else was analysed. Results: (a) **Uncontrolled variables are stable.**
+6. **Stability across releases (tracts and counties, 2015-2019 vs 2020-2024).** One 2015-2019 file,
+   Michigan tract total population (`2019/data/5-year/140/B01003_26.csv.zip`), is refused by census.gov's
+   firewall ('Request Rejected', support ID 13979921158196382640) for every client, while every other
+   2019 tract file, including New York's B01003_36 from the same directory, downloads normally. Its only
+   line is read instead from line 1 ("Total:") of the same release's Michigan tract B01001 file
+   (B01001_26; see Data: substituted files). The two lines are the same total population: in the New York
+   2015-2019 tract files B01003 line 1 and B01001 line 1 agree in ESTIMATE, MOE and all 80 replicates for
+   all 4,918 tracts (0 differing cells), a check re-run by tests/test_replicate_live.py. All variables are
+   therefore analysed in both states and releases. Results: (a) **Uncontrolled variables are stable.**
    Poverty count, poverty rate, owner share and median income stay at 0 to within +/-0.005 at every order
    in both states and releases; of 108 tract class comparisons for them, 3 differ by more than 2 combined
-   SEs (about 5 expected by chance; largest |z| 2.5, all differences <= 0.004). (b) **Population (New
-   York) is stable**: order 1 -0.039 [-0.060, -0.018] in 2015-2019 vs -0.040 [-0.060, -0.020] (within
-   county -0.042 vs -0.043), the same fast decay, a county aggregation ratio of 0.000 again (tract errors
-   sum to zero within a county), and split-half pair reliability 0.60 (2020-2024: 0.61). (c)
+   SEs (about 5 expected by chance; largest |z| 2.5, all differences <= 0.004). (b) **Population is stable
+   in both states.** New York: order 1 -0.039 [-0.060, -0.018] in 2015-2019 vs -0.040 [-0.060, -0.020]
+   (within county -0.042 vs -0.043), the same fast decay, a county aggregation ratio of 0.000 again (tract
+   errors sum to zero within a county), and split-half pair reliability 0.60 (2020-2024: 0.61). Michigan
+   (B01001 line 1): order 1 -0.066 [-0.088, -0.044] vs -0.071 [-0.090, -0.052]; within county -0.075
+   [-0.103, -0.046] vs -0.081 [-0.106, -0.056]; across county -0.005 [-0.014, 0.004] vs +0.003 [-0.007,
+   0.014]; order 2 within county -0.019 vs -0.018; rook vs corner-only -0.075 vs -0.028 (2020-2024: -0.080
+   vs -0.029); aggregation ratio 0.000 in both releases; split-half pair reliability at order 1 0.64
+   (2020-2024: 0.67). Every Michigan population class difference between releases is at most 0.008
+   (order 1 across county, 1.1 combined SEs). As in 2020-2024, Michigan's within-county order-1 correlation is nearly twice New York's. (c)
    **Households change sign.** Occupied housing units (B25003_001) in 2015-2019 have *positive* mean r
    between neighbouring tracts in the same county - Michigan order 1 +0.025 [0.016, 0.033] (within county
    +0.028), New York +0.012 [0.003, 0.020] - against -0.025 and -0.015 in 2020-2024 (differences 8.4 and
@@ -873,8 +895,8 @@ def interpret(df, extras, years):
   stress tests outside the observed range, not plausible ACS conditions for these variables; the
   realistic end of the grid is -0.1..0.05. Correlated-error scenarios with large positive rho should be
   stated as hypothetical (for example for variables or survey designs not studied here).
-* Limits: two states, two releases at tract level (2015-2019 without Michigan population: firewall
-  rejection of that one file), 80 replicates (about 77 effective), and counties as a proxy for weighting
+* Limits: two states, two releases at tract level (2015-2019 Michigan population read from B01001 line
+  1, verified identical to B01003 line 1; Findings 6), 80 replicates (about 77 effective), and counties as a proxy for weighting
   areas. The 95% |r| of 0.23 for a single pair means no individual pair can be
   flagged; only class means are evidence.
 """
diff --git a/tests/test_http.py b/tests/test_http.py
index 0e6cdf6..e5cc18a 100644
--- a/tests/test_http.py
+++ b/tests/test_http.py
@@ -158,7 +158,8 @@ def test_one_delayed_retry_then_clear_error(self):
         page = FakeResponse(REJECTED_PAGE, headers={"Content-Type": "text/html"})
         s = FakeSession([page, page, FakeResponse(b"never reached")])
         with self.assertRaises(rp.VREDownloadError) as ctx:
-            rp.fetch_vre("B01003", 2019, "tract", "26", session=s, cache_dir=self.tmp, check_moe=False)
+            rp.fetch_vre("B01003", 2019, "tract", "26", session=s, cache_dir=self.tmp, check_moe=False,
+                         allow_substitute=False)  # the B01001 substitute: tests/test_replicate.py
         exc = ctx.exception
         path = os.path.join(self.tmp, "140", "B01003_26.csv.zip")
         self.assertEqual(len(s.calls), 2)  # never loops
diff --git a/tests/test_replicate.py b/tests/test_replicate.py
index 7aba26a..374c745 100644
--- a/tests/test_replicate.py
+++ b/tests/test_replicate.py
@@ -563,5 +563,157 @@ def test_pre_2018_has_no_csv(self):
         self.assertEqual(session.calls, [])
 
 
+
+REJECTED_PAGE = (b"<html><head><title>Request Rejected</title></head><body>The requested URL was rejected. "
+                 b"Your support ID is: 13979921158196382640<br><br></body></html>")
+
+
+def _vre_zip(table, title, lines, seed=0):
+    """Synthetic 2019 tract VRE zip for Michigan: ``lines`` = [(ORDER, TITLE)], 3 tracts, MOEs consistent."""
+    rng = np.random.default_rng(seed)
+    head = ["TBLID", "GEOID", "NAME", "ORDER", "TITLE", "ESTIMATE", "MOE", "CME", "SE"] + [
+        f"Var_Rep{i}" for i in range(1, 81)]
+    out = [",".join(head), f"{table},,,,{title}" + "," * (len(head) - 5),
+           f"{table},,,,Universe:  Total population" + "," * (len(head) - 5)]
+    for k in range(3):
+        for order, ltitle in lines:
+            est = 1000 + 300 * k + 10 * order
+            reps = est + rng.integers(-60, 61, 80)
+            se = math.sqrt(4.0 / 80.0 * float(np.sum((reps - est) ** 2)))
+            moe = round(Z90 * se)
+            out.append(",".join([table, f"14000US2616300{k}100", f"\"Census Tract {k}, Wayne County, Michigan\"",
+                                 str(order), ltitle, str(est), str(moe), f"+/-{moe}", str(round(se))]
+                                + [str(int(r)) for r in reps]))
+    buf = io.BytesIO()
+    with zipfile.ZipFile(buf, "w") as zf:
+        zf.writestr(f"{table}_26.csv", "\n".join(out) + "\n")
+    return buf.getvalue()
+
+
+class TestTotalFallback(unittest.TestCase):
+    """B01003 line 1 <- B01001 line 1 when census.gov rejects (or 404s) the B01003 file."""
+
+    def setUp(self):
+        self.tmp = tempfile.mkdtemp()
+        self.url3 = rp.vre_url("B01003", 2019, "tract", "26")
+        self.url1 = rp.vre_url("B01001", 2019, "tract", "26")
+        # Identical pair: same seed, same line-1 values; B01001 has more lines after line 1.
+        self.b01003 = _vre_zip("B01003", "TOTAL POPULATION", [(1, "Total")], seed=3)
+        self.b01001 = _vre_zip("B01001", "SEX BY AGE", [(1, "Total")], seed=3)
+        self.b01001 = self._add_lines(self.b01001)
+
+    def tearDown(self):
+        shutil.rmtree(self.tmp, ignore_errors=True)
+
+    @staticmethod
+    def _add_lines(raw):
+        """B01001 copy whose line 1 is titled 'Total:' and which has a line 2 per tract."""
+        with zipfile.ZipFile(io.BytesIO(raw)) as zf:
+            rows = zf.read("B01001_26.csv").decode().rstrip("\n").split("\n")
+        out = rows[:3]
+        for r in rows[3:]:
+            out.append(r.replace(",1,Total,", ",1,Total:,"))
+            parts = r.replace(",1,Total,", ",2,Male:,").split(",")
+            out.append(",".join(parts))
+        buf = io.BytesIO()
+        with zipfile.ZipFile(buf, "w") as zf:
+            zf.writestr("B01001_26.csv", "\n".join(out) + "\n")
+        return buf.getvalue()
+
+    def _fetch(self, session, **kw):
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("always")
+            frame = rp.fetch_vre("B01003", 2019, "tract", "26", session=session, cache_dir=self.tmp, **kw)
+        return frame, [str(w.message) for w in caught]
+
+    def _check_substituted(self, frame, msgs, reason):
+        sub = frame.attrs["substitution"]
+        self.assertEqual(sub["requested_table"], "B01003")
+        self.assertEqual(sub["requested_url"], self.url3)
+        self.assertEqual(sub["source_table"], "B01001")
+        self.assertEqual(sub["lines"], {"B01003_001": "B01001_001"})
+        self.assertEqual(sub["source_url"], self.url1)
+        self.assertEqual(sub["source_sha256"], hashlib.sha256(self.b01001).hexdigest())
+        self.assertIn(reason, sub["reason"])
+        self.assertIn("0 differing cells", sub["verification"])
+        self.assertEqual(frame.attrs["source_url"], self.url1)  # the file actually read
+        self.assertEqual(frame.attrs["sha256"], sub["source_sha256"])
+        self.assertEqual(frame.attrs["table"], "B01003")
+        self.assertTrue(frame.attrs["notes"][0].startswith("substituted_source:"))
+        self.assertTrue(any("substitute" in m and self.url1 in m for m in msgs))  # never silent
+        self.assertEqual(set(frame["variable"]), {"B01003_001"})
+        self.assertEqual(set(frame["title"]), {"Total"})
+        self.assertTrue(frame.attrs["moe_check"]["passed"])
+        # The B01003 path holds nothing: the substitute is not cached under the requested name.
+        self.assertFalse(os.path.exists(os.path.join(self.tmp, "140", "B01003_26.csv.zip")))
+
+    def test_rejection_uses_b01001_with_provenance(self):
+        page = FakeResponse(REJECTED_PAGE, ctype="text/html")
+        frame, msgs = self._fetch(FakeSession({self.url3: page, self.url1: FakeResponse(self.b01001)}))
+        self._check_substituted(frame, msgs, "13979921158196382640")
+        self.assertEqual(frame.attrs["substitution"]["support_id"], "13979921158196382640")
+        self.assertIsNone(frame.attrs["substitution"]["http_status"])
+
+    def test_404_uses_b01001(self):
+        frame, msgs = self._fetch(FakeSession({self.url1: FakeResponse(self.b01001)}))
+        self._check_substituted(frame, msgs, "404")
+        self.assertEqual(frame.attrs["substitution"]["http_status"], 404)
+        # Cached B01001 is reused on the next call (B01003 is requested again, then B01001 from the cache).
+        s2 = FakeSession({})
+        again, _ = self._fetch(s2)
+        self.assertEqual(s2.calls, [self.url3])
+        pd.testing.assert_frame_equal(again, frame)
+
+    def test_relabelled_frame_equals_b01003_frame(self):
+        direct = rp.fetch_vre("B01003", 2019, "tract", "26", cache_dir=self.tmp,
+                              session=FakeSession({self.url3: FakeResponse(self.b01003)}))
+        shutil.rmtree(os.path.join(self.tmp, "140"))
+        frame, _ = self._fetch(FakeSession({self.url1: FakeResponse(self.b01001)}))
+        pd.testing.assert_frame_equal(frame, direct, check_like=False)
+
+    def test_substitute_unavailable_raises_original_error(self):
+        page = FakeResponse(REJECTED_PAGE, ctype="text/html")
+        with self.assertRaises(rp.VREDownloadError) as ctx:
+            self._fetch(FakeSession({self.url3: page}))  # B01001: 404
+        self.assertTrue(ctx.exception.rejected)
+        self.assertEqual(ctx.exception.url, self.url3)
+        self.assertIn("13979921158196382640", str(ctx.exception))
+        with self.assertRaises(rp.VREDownloadError) as ctx:
+            self._fetch(FakeSession({}))
+        self.assertIn(self.url3, str(ctx.exception))
+
+    def test_other_lines_tables_and_opt_out_do_not_fall_back(self):
+        page = FakeResponse(REJECTED_PAGE, ctype="text/html")
+        session = FakeSession({self.url3: page, self.url1: FakeResponse(self.b01001)})
+        with self.assertRaises(rp.VREDownloadError) as ctx:
+            self._fetch(session, lines=[1, 2])
+        self.assertIn("No verified substitute", str(ctx.exception))
+        self.assertIn("[2]", str(ctx.exception))
+        self.assertNotIn(self.url1, session.calls)
+        with self.assertRaises(rp.VREDownloadError):
+            self._fetch(session, allow_substitute=False)
+        self.assertNotIn(self.url1, session.calls)
+        url = rp.vre_url("B01001", 2019, "tract", "26")
+        with self.assertRaises(rp.VREDownloadError):  # B01001 itself has no substitute
+            rp.fetch_vre("B01001", 2019, "tract", "26", session=FakeSession({url: page}), cache_dir=self.tmp)
+        # Line 1 requested explicitly: substitute used.
+        frame, _ = self._fetch(session, lines=[1])
+        self.assertIn("substitution", frame.attrs)
+
+    def test_other_failures_do_not_fall_back(self):
+        session = FakeSession({self.url3: FakeResponse(b"", status=500, ctype="text/html"),
+                               self.url1: FakeResponse(self.b01001)})
+        with self.assertRaises(rp.VREDownloadError) as ctx:
+            self._fetch(session)
+        self.assertIn("HTTP 500", str(ctx.exception))
+        self.assertNotIn(self.url1, session.calls)
+
+    def test_lines_filter_without_substitution(self):
+        session = FakeSession({self.url1: FakeResponse(self.b01001)})
+        frame = rp.fetch_vre("B01001", 2019, "tract", "26", session=session, cache_dir=self.tmp, lines=[2])
+        self.assertEqual(set(frame["variable"]), {"B01001_002"})
+        self.assertNotIn("substitution", frame.attrs)
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/tests/test_replicate_live.py b/tests/test_replicate_live.py
index 04cf4f6..102a5f2 100644
--- a/tests/test_replicate_live.py
+++ b/tests/test_replicate_live.py
@@ -64,6 +64,23 @@ def test_gzip_release(self):
         self.assertTrue(check["passed"], check)
         self.assertEqual(check["controlled_rows"], 52)  # state total population is controlled
 
+    def test_b01003_total_equals_b01001_total(self):
+        """Basis of the B01003 <- B01001 substitute (census.replicate.VRE_TOTAL_FALLBACKS): line 1 identical."""
+        from census.replicate import REPLICATE_COLUMNS
+
+        kw = dict(check_moe=False, allow_substitute=False)
+        b3 = self._fetch("B01003", 2019, "tract", state_code="36", **kw)
+        b1 = self._fetch("B01001", 2019, "tract", state_code="36", lines=[1], **kw)
+        self.assertNotIn("substitution", b3.attrs)
+        self.assertEqual(len(b3), len(b1))
+        self.assertGreater(len(b3), 4000)
+        cols = ["GEOID", "NAME", "estimate", "moe", "se_published", "controlled"] + REPLICATE_COLUMNS
+        left = b3.set_index("GEOID", drop=False)[cols].sort_index()
+        right = b1.set_index("GEOID", drop=False)[cols].sort_index()
+        self.assertTrue(left.index.equals(right.index))
+        differing = int(((left != right) & ~(left.isna() & right.isna())).to_numpy().sum())
+        self.assertEqual(differing, 0)
+
     def test_published_table_list_matches_registry(self):
         from census.replicate import vre_tables