IESET.
Hypotheses·distribution·tax_inequality_tcja_2017_decile_incidence

The Tax Cuts and Jobs Act 2017 produced after-tax income gains that were monotonically increasing in pre-tax income decile through 2019, with the top decile capturing more than 35 percent of cumulative after-tax income gain over 2018-2019 — orthogonal to the existing TCJA growth-effect spec which targets aggregate output.

The discriminating test is the share of the after-tax-income-gain pie captured by deciles 9-10 vs deciles 1-5, using JCT/CBO distributional tables and CEX/SCF microdata.

PARTIALengine/runs/tax_inequality_tcja_2017_decile_incidence

PARTIAL — shape=pre_post, sign matches but magnitude below threshold; |Δ_log|=0.07; threshold 35.0%, observed 7.0%

confidence cueThe result is useful, but not decisive. Treat it as a clue, not a settled conclusion.

policy briefMixed or noisy

In ordinary language

Over a long period, do more market-oriented institutions translate into higher income or productivity, once the comparison looks beyond a single success story?

plain answer

The evidence is suggestive but not decisive. shape=pre_post, sign matches but magnitude below threshold; |Δ_log|=0.07; threshold 35.0%, observed 7.0%

why it matters

Distributional claims often sound morally clear but are empirically complex. This test asks whether the proposed channel explains real differences across places.

how the test works

It compares 1 country or place units from 2015 to 2020, using a descriptive design.

what was measured
What changed
  • Tcja 2018 post indicator
  • Top marginal income tax rate
What we checked
  • Top decile after tax income share
  • Top 1pct pretax income share
  • Inequality disposable income
what this does not prove

A single test is not the whole truth. It narrows the claim under a specific sample, time period, and method. Strong policy conclusions need the pattern to survive nearby tests, alternative data, and serious objections.

verification

No evidence packet has been generated yet.

Results

engine/runs/tax_inequality_tcja_2017_decile_incidence
1007550250201520182020USA
illustrative sketch · run pending
No coefficients yet. When the model fires, this chart will show top_decile_after_tax_income_share across 1 sampled countries over 2015–2020.
The shapes above are stylised — none of the lines are real data.
Placeholder for tax_inequality_tcja_2017_decile_incidence. Published chart will be generated from engine/runs/tax_inequality_tcja_2017_decile_incidence/chart_data.json.

Pre-registration

pre-registered
first-spec commit 098ce96 · 2026-04-30T12:57:33Z
run generated · 2026-04-30T10:11:18Z

The Tax Cuts and Jobs Act 2017 produced after-tax income gains that were monotonically increasing in pre-tax income decile through 2019, with the top decile capturing more than 35 percent of cumulative after-tax income gain over 2018-2019 — orthogonal to the existing TCJA growth-effect spec which targets aggregate output. The discriminating test is the share of the after-tax-income-gain pie captured by deciles 9-10 vs deciles 1-5, using JCT/CBO distributional tables and CEX/SCF microdata.

Falsification criterion — what would disprove this

set before the run · honoured after

This hypothesis is considered falsified if:

SUPPORTED if top-decile share of cumulative after-tax-income gain over 2018-2019 exceeds 35 percent AND the gradient (decile 10 minus decile 1 percentage-point change in after-tax income) exceeds 1.5 percentage points at p<0.10. REFUTED if top-decile share is below 25 percent or the gradient is below 0.5 percentage points at p<0.10.

formal test & threshold
test:      US descriptive panel of after-tax income change by decile 2017-2019 using TPC/JCT distributional tables, cross-validated with CEX-SCF microdata.

Method

Template
descriptive
Sample
1 countries · 2015 – 2020
Evidence type
descriptive

Descriptive comparison of top-decile vs bottom-decile after-tax income change pre vs post 2018. Cross-validated against TPC/JCT distributional tables. Robustness with event_study around 2018Q1 break.

Data

VariableSourceTransform
top_decile_after_tax_income_share
outcome
owid:top-10-share-of-total-incometier 2
level
top_1pct_pretax_income_share
outcome
owid:top-1-share-of-total-incometier 2
level
gini_disposable_income
outcome
world_bank_wdi:SI.POV.GINItier 2
level
tcja_2018_post_indicator
treatment
constructed:indicator = 1 for year >= 2018tier 5
indicator
top_marginal_income_tax_rate
treatment
owid:top-marginal-income-tax-ratetier 2
level
log_real_gdp
control
fred:GDPC1tier 1
log
unemployment_rate
control
fred:UNRATEtier 1
level

● ready  · ● pending  · ● reconstruct-needed

Detailed result card

Result card — tax_inequality_tcja_2017_decile_incidence

Verdict: PARTIAL — shape=pre_post, sign matches but magnitude below threshold; |Δ_log|=0.07; threshold 35.0%, observed 7.0%

Pre-registration

  • Claim: The Tax Cuts and Jobs Act 2017 produced after-tax income gains that were monotonically increasing in pre-tax income decile through 2019, with the top decile capturing more than 35 percent of cumulative after-tax income gain over 2018-2019 — orthogonal to the existing TCJA growth-effect spec which targets aggregate output. The discriminating test is the share of the after-tax-income-gain pie captured by deciles 9-10 vs deciles 1-5, using JCT/CBO distributional tables and CEX/SCF microdata.
  • Falsification rule: SUPPORTED if top-decile share of cumulative after-tax-income gain over 2018-2019 exceeds 35 percent AND the gradient (decile 10 minus decile 1 percentage-point change in after-tax income) exceeds 1.5 percentage points at p<0.10. REFUTED if top-decile share is below 25 percent or the gradient is below 0.5 percentage points at p<0.10.
  • Falsification test: US descriptive panel of after-tax income change by decile 2017-2019 using TPC/JCT distributional tables, cross-validated with CEX-SCF microdata.

Comparison

  • shape: pre_post
  • country: USA
  • cut_year: 2017
  • pre_mean: 38.47222222222223
  • post_mean: 41.2625
  • delta: 2.7902777777777743
  • log_delta: 0.07001761701398213
  • n_pre: 54
  • n_post: 8

Extracted threshold: {'percent': 35.0}

Variables resolved

  • world_bank_wdi:SI.POV.GINI → gini_disposable_income (outcome, publisher=world_bank_wdi, n=2430)

Variables missing data

  • owid:top-10-share-of-total-income (outcome, name=top_decile_after_tax_income_share)
  • owid:top-1-share-of-total-income (outcome, name=top_1pct_pretax_income_share)
  • constructed: indicator = 1 for year >= 2018 (treatment, name=tcja_2018_post_indicator)
  • owid:top-marginal-income-tax-rate (treatment, name=top_marginal_income_tax_rate)
  • fred:GDPC1 (controls, name=log_real_gdp)
  • fred:UNRATE (controls, name=unemployment_rate)

Generated by scripts/run_descriptive.py at 2026-04-30T10:11:18+00:00

Notes

Tax-inequality candidate, swarm-S6 batch 2. Orthogonal angle to existing fiscal/tcja_2017_growth_effect.yaml — tests incidence by decile rather than aggregate output.

Authored framework. Read the transparency note.