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MaxGhenis merged 8 commits into from
Sep 13, 2026
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Introduce SPM threshold methods in active prose #7

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12712fa
Present SPM methods with direct prose and preserve forecast evidence
MaxGhenis Sep 13, 2026
5dd0aac
Define geographic diagnostics and table tenure order
MaxGhenis Sep 13, 2026
20bfbe1
Record forecast amendment date and registration identities
MaxGhenis Sep 13, 2026
c050d91
Keep forecast registration evidence beside the validation claim
MaxGhenis Sep 13, 2026
c0e6633
Verify fixed supporting records and clarify forecast evidence
MaxGhenis Sep 13, 2026
73d1cd7
Clarify pooled expenditure selection and primary forecast choice
MaxGhenis Sep 13, 2026
9e94bd1
Check the superseded forecast footnote against its archived score
MaxGhenis Sep 13, 2026
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Keep forecast record text distinct from yearly scenario records
MaxGhenis Sep 13, 2026
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124 changes: 48 additions & 76 deletions README.md
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# Calculating and projecting Supplemental Poverty Measure thresholds

[Manuscript source](paper/index.qmd) ·
[Data provenance](data/PROVENANCE.md) ·
[Pinned companion calculator](https://github.com/PolicyEngine/spm-calculator/tree/78bae15f76152c6076dd909a09f6b63dc2ec8c34)

Working paper on national SPM threshold estimation from public Consumer
Expenditure Survey microdata, family and geographic adjustments, and
projection from consumption and price growth. The manuscript presents
current-method replication and sample sensitivities, retrospective
comparisons, and a separately preserved pre-committed 2025 validation.
It also constructs conditional forecasts through 2035 by advancing the
CE and ACS windows with explicit price, real-spending, and rent assumptions.

The current six-year results use revised inputs and overlapping CE
windows. They are separate from the single prospective validation year.
Method limitations and the forecast amendment history are reported in
the manuscript. The repository preserves source artifacts, method
versions, and forecast commitment evidence.
[Read the paper](https://spm-threshold-paper.vercel.app/) ·
[Download the PDF](https://spm-threshold-paper.vercel.app/index.pdf) ·
[Manuscript source](paper/index.qmd)

The Bureau of Labor Statistics calculates Supplemental Poverty Measure (SPM)
thresholds from spending on basic needs. The U.S. Census Bureau adjusts them
for family composition and local housing costs. We reconstruct national
thresholds from public Consumer Expenditure (CE) Survey data and compare four
projection rules. We evaluate retrospective projections and a pre-committed
2025 nowcast, then project thresholds through 2035 by advancing the CE and
American Community Survey (ACS) windows. We specify prices, real spending,
and rents for the future scenarios and evaluate prospective accuracy for
2025 only.

## Build and verify

Expand All @@ -29,64 +25,40 @@ quarto render --to pdf

The guard and table generators use the Python standard library. Quarto
1.9.36 and TeX Live 2026 render the HTML and PDF to `_output/paper/`.
Clone with full tag history and check out the exact revision to reproduce
it. The guard first checks artifact hashes and frozen Git identities,
then generates tables and evaluation JSON in temporary storage and
compares every output byte with the checkout, including archived tables
that the manuscript no longer includes. It never repairs or
restores source artifacts. The regression tests verify that failed checks
leave source bytes unchanged.

This is an artifact-level verification: it re-derives tables from the
preserved experimental outputs. The [experiment replay guide](docs/reproducing-experiments.md)
gives executable commands, source links, and input prerequisites separately
for the 0.5.0 retrospective CE experiment and the 1.0.0 rolling CE/ACS
projection. The historical population sensitivity lacks
immutable model and dataset identities, so exact replay of that result
has not been established. No published package or deployed application is
required to render the paper.

## Preserved forecast evidence

The tags `v1.0-original-nowcast` and `v1.1-amended-nowcast`, forecast
bytes, and all original OpenTimestamps manifest/proof pairs are preserved.
Two hashes in `data/COMMITMENT-MANIFEST.txt` were incorrect; the dated
`data/COMMITMENT-AMENDMENT-2026-09-08.txt` records the exact tag hashes and
the original manifest digest. The original proof does not cover that
amendment. This revision verifies retained proof bytes and Git identities;
it does not independently reverify blockchain attestations.

`data/SHA256SUMS` continues to cover only the frozen artifacts. New inputs
have their own `data/current/SHA256SUMS`; they do not replace the frozen
forecast or become a new prospective commitment. `data/PROVENANCE.md`
describes both collections and the original implementation pin.

## September 11, 2026 development poverty-rate prediction

**Status as of September 13, 2026:** these development estimates remain
provisional pending a comparison on the final, qualified model and
population release. They are separate from the paper's threshold-method
results.

`data/predictions/2025-spm-poverty-rates-2026-09-11.json` records, before the
Census Bureau's 2026-09-15 release, a pre-committed prediction for the 2025 SPM
poverty rate: the Census 2024 rate plus the modeled 2024-to-2025 change under
the rolling CE and ACS threshold method (13.2 percent overall on the corrected
2024 series; 14.3 for children; 14.6 for people 65 and over). Its SHA-256 is in
`data/predictions/SHA256SUMS` and the OpenTimestamps proof is beside it. The
file is never edited; any revision is a dated amendment file.

## Companion implementation

The companion spm-calculator provides a portable artifact, standalone
unit calculations, CE research replication, rolling projections, and
PolicyEngine, Microcosm, and native Axiom adapters. The rolling projection
pins the 1.0.0 release candidate at commit
`78bae15f76152c6076dd909a09f6b63dc2ec8c34`, with content digest
Clone with full tag history and check out the desired source commit.
The guard checks input hashes and forecast registrations, generates tables
and evaluation JSON in temporary storage, and compares outputs with the
recorded files. The tests check that input corruption fails verification
without changing source bytes.

The [experiment replay guide](docs/reproducing-experiments.md) supplies
commands, source links, and input requirements for the CE and ACS estimators.
The [data provenance](data/PROVENANCE.md) identifies each experimental
collection. The [forecast record](docs/forecast-record.md) provides the
registration evidence and supporting evaluations. These files distinguish
table verification from replication of the underlying survey estimates.

## Companion calculator

[SPM Calculator](https://github.com/PolicyEngine/spm-calculator) provides
standalone unit calculations, CE replication, rolling forecasts, and adapters
for PolicyEngine, Microcosm, and the Axiom rules engine. The paper and calculator
consume the same rolling projection artifact: version 1.0.0 release candidate
at commit `78bae15f76152c6076dd909a09f6b63dc2ec8c34`, with content digest
`3d86d5c4c0423480e6b69b75d222ffa4a7a2639e4094df5ba2504af01be17173`.
The paper consumes the same projection bytes as the calculator.

The 2019–2025 retrospective experiment retains its separate development
version 0.5.0 pin at `0d7fa0d77b0a88064ab7b9fe70557309b5f7901f`.
These source identities document reproducibility; they do not certify
publication, deployment, or a population-model migration.
The 2019–2025 retrospective experiment uses a separate implementation:
version 0.5.0 at commit
`0d7fa0d77b0a88064ab7b9fe70557309b5f7901f`.

## Separate 2025 poverty-rate prediction

The [September 11 prediction](data/predictions/2025-spm-poverty-rates-2026-09-11.json)
predicts a 2025 SPM poverty rate of 13.2 percent overall, 14.3 percent
for children, and 14.6 percent for people 65 and over. The registration
precedes the Census release scheduled for September 15, 2026. It adds
the modeled 2024-to-2025 change to Census's
2024 rate. These development estimates remain provisional pending a
comparison on the qualified model and population release. The threshold-method
results do not depend on them. The prediction's checksum and timestamp proof
accompany the file; any subsequent estimate receives its own dated record.
44 changes: 44 additions & 0 deletions docs/forecast-record.md
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# Forecast registration and evaluation record

## Forecast chronology

The 2025 commitment used a price calculation that combined CPI components
with different index bases. We corrected the calculation before BLS published the outcome, and the
equal blend remained the primary forecast.
We amended the forecast on July 18, 2026. The correction changed the
retrospective ranking, placing the consumption growth rule first. The
evaluation retained every component rule.

The correction moved estimates by 0.1 to 0.3 percent. In tenure order, the
original and amended forecasts were:

| Tenure | Original forecast | Amended forecast |
|---|---:|---:|
| Owners with mortgages | $41,099.57 | $41,036.34 |
| Owners without mortgages | $34,250.70 | $34,135.99 |
| Renters | $40,791.72 | $40,755.98 |

The original and amended values, corrected 2024 base, and evaluation rules
remain fixed in the repository. The preregistration records the forecast
values and evaluation rules before the outcome ([Nosek et al., 2018](https://doi.org/10.1073/pnas.1708274114)).

The [August 7, 2026 archived page](https://web.archive.org/web/20260807211521/https://spm-threshold-paper.vercel.app/)
and retained OpenTimestamps evidence precede the August 24 publication.
The archive shows both forecast sets. The repository preserves them at
tags `v1.0-original-nowcast` and `v1.1-amended-nowcast`, with their
manifests and proof files. Both GitHub releases date to August 7, 2026. A September 8 amendment corrects two hashes in a secondary manifest;
the original timestamp does not cover that amendment. The verification
script checks retained bytes and Git identities without independently
reverifying blockchain attestations.

## Evaluation record

The original blend scored 0.98 percent mean absolute error, compared with
1.17 percent for the amended primary blend. The complete historical
evaluation, including the superseded original blend, remains in
[`paper/tables/evaluation.md`](../paper/tables/evaluation.md). The generator also produces the primary four-rule table at
[`paper/tables/evaluation_main.md`](../paper/tables/evaluation_main.md).
The underlying evaluation artifact is
[`data/evaluation_2025.json`](../data/evaluation_2025.json), and the
forecast inputs and preserved commitment evidence remain in the
[`data/`](../data/) artifacts.
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