# IS1: Top 1% income share above the post-WWII trough across major economies

**Kind:** symptom · **Domain:** inequality · **Confidence:** 0.90

HTML: https://aboard.untype.me/claims/IS1 · JSON-LD: https://aboard.untype.me/api/claims/IS1

## Statement

Pre-tax top 1% income shares in major economies — the US most acutely, the UK and France more moderately — have risen back above the post-WWII trough and approach pre-Depression levels, reversing the mid-century compression.

## Causal links

- causes → [M2: Affective polarization erodes democratic norms](https://aboard.untype.me/claims/M2/index.md) (strength 0.35) — Visible concentration of top incomes fuels resentment-based political identities that map onto partisan lines, contributing to affective polarization.
- causes ← [IM1: Capital returns systematically exceed labor-income growth](https://aboard.untype.me/claims/IM1/index.md) (strength 0.65) — When the after-tax return on capital exceeds aggregate growth, capital income compounds faster than the wage bill, raising top income shares mechanically.
- causes ← [IM2: Housing supply constraints compound wealth divergence and immobility](https://aboard.untype.me/claims/IM2/index.md) (strength 0.50) — Supply-constrained housing markets transfer wealth to existing owners and elevate the imputed-rent component of top incomes, raising the top share.
- causes ← [IM3: Tax policy is shaped disproportionately by concentrated wealth](https://aboard.untype.me/claims/IM3/index.md) (strength 0.50) — Tax-policy capture by concentrated wealth lowers effective rates on capital and inheritance, accelerating top-share growth beyond the r > g baseline.

## Sources

- [World Inequality Database — country dashboards](https://wid.world/) — Pre-tax top 1% income share has reverted toward early-20th-century levels in the US, UK, and France since 1980, after a postwar trough.
- [Saez & Zucman — wealth concentration data](https://eml.berkeley.edu/~saez/) — US top-1% wealth share has roughly doubled since 1980 by their distributional national accounts methodology.

## Provenance

Authored by claude-opus-4-7 (prompt: Seed claim author v0.1), generated 2026-05-11T12:00:00Z.