NBER's Norway Verdict (2021–2025): Flight Is Real but Cost Only ~3.5 Points of a 75% Revenue Gain
The strongest peer-review-track evidence yet on wealth-tax feasibility landed this month: Marius Ring, "Taxing Entrepreneurial Wealth: Evidence from Norway, 2021–2025," NBER Working Paper 35854 (issue date October 2026). It exploits Norway's 2021–2024 reform sequence — higher dividend tax rates, closure of migration-related capital-gains loopholes, and a near-doubling of the effective marginal tax rate on business wealth — the same package that produced the Financial Times' "exodus of Norwegian billionaires" narrative in 2023.
The findings, from the abstract itself (NBER w35854):
- Flight is real but narrow: "While I document clear effects on migration, these responses are concentrated among the top 0.1% of the wealth distribution and mostly confined to 2022 and 2023. My results indicate that at most 100 individuals left due to the reforms."
- The revenue cost of that flight is small: "I estimate that absent any outmigration, wealth tax revenues would have increased by 75% from 2021 to 2024. Reform-driven outmigration lowers the revenue gain to 71.5%.1"
- No talent or firm effects: "I find no evidence of significant outmigration or reduced inflows of startup founders or inventors… outmigrating owners' firms remain economically active and do not reduce investment," and across Norwegian- vs foreign-owned firm comparisons, "no evidence that Norwegian-owned firms pay out more dividends or invest less after the reforms, nor is there any evidence that the reform induced more bankruptcies."
- Bottom line, in the author's words: "the short-run economic costs of wealth taxation, in terms of migration and firm investment, are more limited than the public debate implies."
What this does to the debate. The headline story — ~300 millionaires and billionaires relocating, mostly to Switzerland — was never in dispute; what Ring adds is the revenue significance: the flight ate roughly 3.5 percentage points of a 75% revenue gain, i.e., under 5% of the expected take. That is direct quantitative ammunition against the strongest version of the capital-flight argument (the Hoover Institution's claim that California's Prop 40 would produce a net loss of $25 billion — see California Proposition 40 Endgame: Newsom Backs the Ban, Hoover Scores a Net Loss, and the FTB War-Room Problem) — with the crucial caveat that Norway's reform was an annual tax at ~1.1% on business wealth, not a one-time 5% levy, and Norway's administrative capacity (full wealth registers, municipal BOD history) is the exception globally, not the rule. The paper's short-run window (through 2025) also can't rule out longer-run effects on firm location or entrepreneurship.
The design lesson travels: migration response concentrated at the very top of the distribution (top 0.1%), where mobility is highest — exactly the population a billionaire-only tax targets — but even there, the observed response did not gut revenue. Whether that survives contact with a 5% rate, or with a state (rather than national) tax in a federation full of zero-wealth-tax alternatives, is the open question the California vote will now speak to.
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An instance of The measured cost of wealth-tax flight is a few points of revenue, not a collapse. — The only rigorous measurement puts flight's revenue cost at roughly 3.5 points of a 75% gain — under 5% of the expected take, with at most ~100 leavers and no firm or founder effects. ↩︎