The Case for Taxing Billionaires: History, Evidence, and Why This Moment Is Different
By Ojas Shrestha
The wealth tax debate is frequently reduced to a binary: redistribution versus incentives, fairness versus efficiency, left versus right. That framing obscures more than it reveals. The more substantive questions - why wealth concentration has reached its current scale, whether existing tax systems are structurally capable of addressing it, and under what conditions a wealth tax becomes administratively and politically viable.
This article attempts that treatment. It draws on Gabriel Zucman's We Need to Tax Billionaires, the May 2026 NBER working paper by Boll, Saez, and Zucman on California billionaire wealth and taxation, and the broader empirical literature on wealth inequality. The aim is not to advocate uncritically for a particular policy position, but to examine the evidence seriously and follow it where it leads.
I. A Brief History of Progressive Taxation
Understanding the contemporary wealth tax debate requires understanding the fiscal architecture that preceded it.
Prior to 1843 in Britain, taxation fell almost entirely on consumption - duties on goods, tariffs on trade, levies on everyday purchases. The structure was inherently regressive: those who spent the greatest proportion of their income (low earning households) bore the greatest tax burden, while accumulated wealth sat largely beyond the reach of the state. The introduction of income tax in 1843 represented the first structural departure from this model - a recognition that fiscal capacity, not merely expenditure, ought to form the basis of contribution.
The next significant rupture came in 1909. Lloyd George's People's Budget introduced a 2.5% "super tax" on the 10,000 wealthiest individuals in the United Kingdom. The political reaction was fierce. The House of Lords initially rejected the legislation. Critics warned that taxation of this kind would destroy capital formation and drive wealth overseas. The rhetoric bore a striking resemblance to contemporary objections: Dickens had already satirised it a generation earlier, with factory owners threatening to “throw their factories into the sea” if taxed. The factories remained. Progressive taxation spread. France enacted an income tax in 1914; the United States followed in 1913 under the Sixteenth Amendment.
What the historical record demonstrates is not that progressive taxation was inevitable, but that it followed a recognisable pattern: accumulating economic inequality, shifting political coalitions, and eventually a first mover whose institutional example others adopted. Zucman's contention in We Need to Tax Billionaires is that this pattern is now repeating - and that the first mover in a new era of wealth taxation is likely to be France.
II. The Scale of Contemporary Wealth Concentration
Before evaluating the case for a wealth tax, it is necessary to establish the empirical magnitude of the phenomenon it is designed to address.
The May 2026 NBER paper by Boll, Saez, and Zucman provides the most granular recent account, focusing on California as a jurisdiction with unusually high billionaire wealth density and detailed publicly available data through SEC filings. The findings are stark.
Since 1982, the real wealth of California's billionaire class - defined as the top 0.0002% of families, approximately 45 households - has increased by a factor of 30. Over the same period, average Californian family income has roughly doubled in real terms. The divergence is not cyclical. Controlling for stock market fluctuations, the underlying trend has been consistently upward for over four decades.
By the end of 2025, 239 California billionaires held combined wealth of $2.05 trillion - equivalent to 48% of California's annual GDP, up from 23% in 2022. The concentration within the billionaire class itself is also notable: the four wealthiest individuals - Larry Page, Sergei Brin, Mark Zuckerberg, and Jensen Huang - account for 43% of total California billionaire wealth, with their fortunes tied almost entirely to the publicly traded equity of Alphabet, Meta, and Nvidia.
The taxation data is equally significant. These four individuals pay, on average, 0.07% of their wealth in California income tax annually. In 2019, 2020, and 2023, Page and Brin paid zero California income tax on their Alphabet stakes, despite their combined share of Alphabet profits running to approximately $20 billion across those three years. Their official compensation from Alphabet: one dollar each per year.
This is not aggressive avoidance in the technical sense. It is the mathematically predictable outcome of applying a realisation-based income tax to individuals whose wealth takes the form of unrealised equity appreciation and who have no material need to liquidate holdings to fund consumption.
The Buy-Borrow-Die Mechanism
The structural mechanism deserves elaboration. Ultra-wealthy individuals need not sell assets to fund expenditure. They borrow against them - using concentrated equity portfolios as collateral for low-interest loans. The proceeds of borrowing are not taxable income. When assets are eventually transferred at death, heirs receive a stepped-up cost basis, and the accumulated unrealised gains - potentially representing decades of appreciation - are extinguished without ever triggering a tax liability.
The Boll-Saez-Zucman paper estimates that at least 80% of California billionaire wealth consists of unrealised capital gains. Under the current realisation-based system, the majority of this wealth will never be subject to income taxation at any point in its existence. The income tax, however progressive its nominal rate structure, is not designed to reach wealth of this character.
III. Wealth as a Social Product
The philosophical foundation of Zucman's argument rests on a claim that has significant implications for how we frame the taxation debate: wealth, particularly at the scale under discussion, is not purely a private achievement. It is a social product.
The returns that accrue to the founders of Alphabet, Meta, and Nvidia were generated within systems of public provision - legal infrastructure enforcing contracts and property rights, publicly funded research institutions whose outputs underpinned the technologies that made these companies possible, regulatory environments that structured market competition, and the collective consumption of millions of households whose demand sustains corporate revenues. ARPANET, the precursor to the internet, was a government project. Much of the foundational research in machine learning that now drives Nvidia's commercial success originated in publicly funded academic institutions.
The implication is not that private enterprise deserves no return. It is that the categorical distinction between private wealth and social contribution - the distinction that frames any claim on accumulated wealth as expropriation - does not withstand scrutiny. If wealth is partly constituted by social conditions, then the question of how society ought to participate in its returns is not a question of redistribution from the deserving to the undeserving. It is a question of how social contributions are appropriately compensated.
There is also a political economy dimension that Zucman treats seriously. In France, billionaires currently own approximately 85% of the private press. The concentration of media ownership in the hands of those with the most to lose from wealth redistribution creates systematic incentives to frame public debate in particular ways - to characterise wealth taxes as threats to employment and growth, and to encourage working-class voters to identify their interests with those of capital rather than labour. This is not a conspiratorial account. It is a rational description of the behaviour of actors with concentrated wealth and the institutional means to shape public discourse.
IV. Why Previous Wealth Taxes Failed - and the Design Principles That Follow
The most intellectually serious objections to wealth taxation are not ideological but practical. They deserve precise treatment, because the failure modes of previous attempts are instructive.
The Problem of Exemptions
France's post-1981 experience is the canonical case. When the Socialist government introduced a wealth tax, it included an exemption for "professional assets" - defined as an ownership stake of more than 25% in a company in which the owner was actively involved. The stated rationale was to protect working entrepreneurs from being compelled to liquidate stakes in their own businesses.
In practice, the exemption was definitionally coextensive with the population it was meant to tax. Virtually every significant billionaire in France qualified. The tax raised negligible revenue relative to its stated ambitions and was eventually repealed. The lesson is straightforward: a wealth tax designed with large categorical exemptions is not a wealth tax. It is a tax on those insufficiently wealthy to qualify for the exemptions.
The California proposal draws this lesson explicitly. The tax base encompasses worldwide net worth - publicly traded equity, private business stakes, financial assets - without exemptions for professional or active assets. The comprehensiveness of the base is not incidental. It is the precondition for the policy functioning as intended. Zucman argues that this design failure accounts for the majority of European wealth tax failures, and that correcting it is the single most important structural decision in any new proposal.
The Migration Concern
The second objection - that taxing billionaires will prompt them to relocate, eliminating future income tax revenue in excess of the wealth tax raised - is more persistent in public debate and requires more careful engagement.
The Boll-Saez-Zucman paper addresses this empirically rather than theoretically. California billionaires pay approximately 0.2% of their wealth in state income tax per year. The proposed one-off 5% wealth tax is a single levy. Under the most extreme scenario - complete, permanent departure of every California billionaire following the tax - it would take 25 years for the cumulative income tax losses to equal the revenue raised by the one-off. The mobility concern does not make the arithmetic negative. It modulates the magnitude of the gain.
For a permanent annual wealth tax, the paper draws on semi-elasticity estimates from Spain (Agrawal, Foremny, and Martínez-Toledano, 2026) and Switzerland (Brülhart et al., 2022) - the two jurisdictions with sub-national wealth taxes for which mobility responses have been empirically estimated. Using a semi-elasticity of 10, consistent with these studies, a 1% permanent annual wealth tax retains approximately 88% of projected revenue after accounting for mobility and associated income tax losses. The revenue loss from mobility is real but not revenue-destroying.
There is also a structural dimension to this question. The United States taxes its citizens on worldwide income regardless of residence. Zucman's proposal extends this logic: if an individual's wealth was accumulated using the assets, institutions, and infrastructure of a particular jurisdiction, that jurisdiction retains a taxable claim on those assets irrespective of subsequent residency decisions. The practical implementation of extraterritorial wealth taxation is complex. It is not technically impossible.
The Valuation Problem
A third objection concerns the difficulty of valuing illiquid or complex assets - private businesses, real estate held through entities, alternative investments. If wealth cannot be reliably valued, it cannot be reliably taxed.
The paper's response is partially empirical: approximately two-thirds of California billionaire wealth is publicly traded equity, valued continuously through market prices and reported to the SEC. For this component, there is no valuation problem of principle. For private business wealth, the California proposal uses formula-based presumptive valuations derived from the capitalisation methodology developed by Saez and Zucman (2016) - the same methodology employed in Swiss cantonal wealth tax administration, which has functioned continuously for over a century. The valuation challenge is genuine but not categorically different from challenges already addressed in existing tax systems.
V. The Shifting Intellectual Consensus
The most consequential recent development in this debate is a shift in the composition of its proponents.
In July 2025, an Op-Ed in Le Monde was signed by seven Nobel Prize-winning economists - among them Joseph Stiglitz, Paul Krugman, and Esther Duflo - alongside Olivier Blanchard, former chief economist of the International Monetary Fund. Their collective position: a 2% minimum annual tax on the super-rich is both necessary and administratively feasible.
Blanchard's presence on that list is significant. His work on fiscal policy and macroeconomic stabilisation has not historically been associated with redistributive advocacy. His endorsement signals that the case for wealth taxation has migrated from the heterodox margins of political economy into the centre of mainstream economic debate. The standard dismissal - that wealth taxation reflects ideology rather than analysis - becomes considerably harder to sustain when the signatories include figures from the ideological centre of the profession.
Zucman's historical analogy is instructive here. The 1909 UK super-tax was followed by comparable measures in France and the United States within five years. The first mover in any wave of fiscal reform creates the institutional template - the administrative mechanisms, the legal frameworks, the empirical record - that subsequent adopters draw on. France is currently the most plausible first mover in a new era of wealth taxation. If a properly designed wealth tax is implemented and functions as the evidence suggests it should, the political and intellectual barriers to adoption elsewhere will fall considerably.
VI. The Counterarguments, Assessed
No intellectually honest treatment of this question can avoid engaging with the strongest objections.
Capital formation. The classical argument against wealth taxation holds that reducing the stock of private capital reduces investment, thereby lowering productivity growth and, ultimately, wages. This is theoretically coherent. The empirical relationship, however, is weaker than the theory implies at the concentrations of wealth under discussion. The four California billionaires at the centre of this analysis hold their wealth primarily as unrealised equity stakes in companies whose investment decisions are driven by corporate retained earnings, strategic priorities, and external financing - not by whether the founder liquidates personal holdings. The link between the personal wealth of billionaire shareholders and productive corporate investment is attenuated.
Incentive effects. Taxing the returns to economic success reduces the incentive to pursue it. This is true in principle. Two qualifications are relevant. First, the magnitude of the effect at the margin is empirically unclear and likely small relative to the non-pecuniary motivations - status, legacy, creative satisfaction - that drive entrepreneurial activity at the highest levels. Second, much of the wealth accumulation under examination results from stock price appreciation that the individuals concerned did not choose or control. A 1% annual wealth tax on a portfolio growing at 20% per year does not materially alter the incentive to build companies.
Administrative feasibility. The concern that sophisticated wealth management will erode the tax base through avoidance is the strongest practical objection, and it deserves to be taken seriously. The response is a design argument rather than a dismissal: a comprehensive base with no categorical exemptions, extraterritorial reach, and strong enforcement mechanisms substantially limits avoidance opportunities. The argument that avoidance is inevitable is an argument for rigorous design, not for abandoning the policy.
Conclusion
Gabriel Zucman opens We Need to Tax Billionaires with three words: "Now's the time." The evidence reviewed here suggests that this assessment is defensible - not on the grounds that the politics are straightforward, but on the grounds that the intellectual, empirical, and institutional conditions for a serious wealth tax are, for the first time in several decades, converging.
The academic consensus is moving. The empirical case for the scale and persistence of wealth concentration is now well-established in the literature. The design failures of previous attempts are understood, and the corrective principles are clearly specified. And the political arithmetic - particularly in France, where the combination of press concentration, visible inequality, and a history of wealth tax debate makes the issue particularly salient - may be approaching the threshold at which legislation becomes viable.
The objections to wealth taxation are not trivial, and they should not be treated as such. The migration concern is real. Capital formation effects deserve rigorous modelling. Administrative implementation is genuinely complex. But the weight of current evidence suggests that a properly designed wealth tax - comprehensive in base, extraterritorial in reach, rigorously enforced - is both administratively feasible and revenue-positive after behavioural responses.
The opponents of Lloyd George's 1909 Budget predicted economic catastrophe. The factories were not thrown into the sea. Progressive income taxation became the fiscal foundation of the twentieth-century state. The question now is whether the twenty-first century will produce an analogous response to an analogous problem - and whether the political institutions of liberal democracies retain the capacity to act on what the evidence recommends.
That question remains open. It is also, I would argue, one of the most important questions in contemporary economic policy.