IESET.
Hypotheses·distribution·tax_inequality_thatcher_1988_top_rate_cut

Nigel Lawson's 1988 budget cut the UK top marginal income tax rate from 60 to 40 percent, producing a discrete jump in the UK top-1 pre-tax national income share within three years that exceeds the contemporaneous G7-ex-UK trajectory.

The UK case is a clean event because the 1988 reform was not paired with substantial base-broadening, so the residual after controlling for the City of London financial deregulation effect should isolate a top-rate-cut-on-distribution effect.

PARTIALengine/runs/tax_inequality_thatcher_1988_top_rate_cut

PARTIAL — mean_gap=+0.06276, |gap|/pre_sd=0.21, p_perm=1 (gap below 0.5×pre_sd or placebo p≥0.10)

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. mean_gap=+0.06276, |gap|/pre_sd=0.21, p_perm=1 (gap below 0.5×pre_sd or placebo p≥0.10)

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 7 country or place units from 1980 to 1995, using a synthetic control design, with fixed effects for country and year.

what was measured
What changed
  • Lawson 1988 uk post
  • Top marginal income tax rate
What we checked
  • Top 1pct pretax income share
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_thatcher_1988_top_rate_cut
1007550250198019881995GBRUSAFRADEUITACANJPN
illustrative sketch · run pending
No coefficients yet. When the model fires, this chart will show top_1pct_pretax_income_share across 7 sampled countries over 1980–1995.
The shapes above are stylised — none of the lines are real data.
Placeholder for tax_inequality_thatcher_1988_top_rate_cut. Published chart will be generated from engine/runs/tax_inequality_thatcher_1988_top_rate_cut/chart_data.json.

Pre-registration

pre-registered
first-spec commit 098ce96 · 2026-04-30T12:57:33Z
run generated · 2026-04-30T12:29:43Z

Nigel Lawson's 1988 budget cut the UK top marginal income tax rate from 60 to 40 percent, producing a discrete jump in the UK top-1 pre-tax national income share within three years that exceeds the contemporaneous G7-ex-UK trajectory. The UK case is a clean event because the 1988 reform was not paired with substantial base-broadening, so the residual after controlling for the City of London financial deregulation effect should isolate a top-rate-cut-on-distribution effect.

Falsification criterion — what would disprove this

set before the run · honoured after

This hypothesis is considered falsified if:

SUPPORTED if UK top-1 pretax share rises by at least 1.5 percentage points 1988-1992 AND DiD coefficient against G6 control pool is positive at p<0.10 after controlling for finance-sector value-added share. REFUTED if UK top-1 share fails to rise by 0.75 percentage points over the window or DiD coefficient is negative at p<0.10.

formal test & threshold
test:      Synthetic-control with G6 donor pool, treated UK 1988. Outcome top-1 pretax share. Auxiliary panel-FE with finance-sector VA-share as confounder control.

Method

Template
synthetic_control
Fixed effects
country, year
Clustering
country
Sample
7 countries · 1980 – 1995
Evidence type
associational

Synthetic-control with G6 donor pool. Treated UK 1988. Placebo-in-time 1985 and 1991 to check sensitivity. Robustness with synth_did.

Data

VariableSourceTransform
top_1pct_pretax_income_share
outcome
owid:top-1-share-of-total-incometier 2
level
lawson_1988_uk_post
treatment
constructed:indicator = 1 for GBR, year >= 1988tier 5
indicator
top_marginal_income_tax_rate
treatment
owid:top-marginal-income-tax-ratetier 2
level
finance_va_share
control
world_bank_wdi:NY.GDP.MKTP.KDtier 2
level
log_real_gdp_per_capita
control
world_bank_wdi:NY.GDP.PCAP.KDtier 2
log
trade_openness
control
world_bank_wdi:NE.TRD.GNFS.ZStier 2
level

● ready  · ● pending  · ● reconstruct-needed

Detailed result card

Result card — tax_inequality_thatcher_1988_top_rate_cut

Verdict: PARTIAL — mean_gap=+0.06276, |gap|/pre_sd=0.21, p_perm=1 (gap below 0.5×pre_sd or placebo p≥0.10)

Pre-registration

  • Claim: Nigel Lawson's 1988 budget cut the UK top marginal income tax rate from 60 to 40 percent, producing a discrete jump in the UK top-1 pre-tax national income share within three years that exceeds the contemporaneous G7-ex-UK trajectory. The UK case is a clean event because the 1988 reform was not paired with substantial base-broadening, so the residual after controlling for the City of London financial deregulation effect should isolate a top-rate-cut-on-distribution effect.
  • Falsification rule: SUPPORTED if UK top-1 pretax share rises by at least 1.5 percentage points 1988-1992 AND DiD coefficient against G6 control pool is positive at p<0.10 after controlling for finance-sector value-added share. REFUTED if UK top-1 share fails to rise by 0.75 percentage points over the window or DiD coefficient is negative at p<0.10.

Synthetic-control estimate

  • shape: synth_did
  • treated_country: GBR
  • event_year: 1988
  • n_donors: 3
  • donor_weights (top): {'CAN': 0.6842, 'FRA': 0.3158, 'USA': 0.0}
  • pre_rmse: 0.3400173872210478
  • pre_period_sd: 0.2991766479300594
  • mean_post_gap: 0.06275531844316595
  • end_period_gap: 0.42630622817874375
  • post_period_years: [1988, 1995]
  • placebo_p_value: 1.0
  • n_placebos: 3
  • method: synthetic-control via NNLS, permutation inference

Variables resolved

  • owid:top-1-share-of-total-income → top_1pct_pretax_income_share (outcome, n=3294)
  • owid:top-marginal-income-tax-rate → top_marginal_income_tax_rate (treatment, n=590)
  • world_bank_wdi:NY.GDP.PCAP.KD → log_real_gdp_per_capita (controls, n=14066)
  • world_bank_wdi:NE.TRD.GNFS.ZS → trade_openness (controls, n=10714)

Generated by scripts/run_synth_did.py at 2026-04-30T12:29:43+00:00

Notes

Tax-inequality candidate, swarm-S6 batch 1. Identification challenge is separating Big Bang 1986 financial deregulation (already underway) from the 1988 rate cut.

Authored framework. Read the transparency note.