On the campaign trail with Gabriel Zucman, the economist who wants to tax California's billionaires

Proposition 40 is a proposed one-time tax on total wealth held by California’s billionaires. It would cover both professional and personal wealth. Voters would decide whether the measure becomes law by answering yes or no during the November 3 midterm elections.

The proposal applies a 5% rate to the wealth of roughly 250 Californian billionaires. Its backers estimate that the measure could raise $100 billion. The money is intended to protect health coverage for 3.5 million Californians facing cuts.

The vote matters because it links a tax on concentrated wealth to an immediate public goal: preserving health coverage. Proposition 40 was put on the ballot after the SEIU-UHW union collected the required 875,000 signatures. The article does not describe the vote’s outcome, so the proposal’s future remains undecided.

The proposed tax would fall on roughly 250 billionaires living in California. It would apply to their total wealth, not only money connected to businesses or jobs. Personal holdings would also be included under the measure described in the article.

The rate would be 5%, charged once against that combined wealth. For example, the proposal treats professional and personal wealth as one tax base rather than separating them. Campaign supporters estimate that this approach would raise $100 billion, although the article does not provide a detailed calculation.

That scale is central to the campaign. The money is intended to preserve health coverage for 3.5 million Californians threatened by cuts. The tax would therefore ask a very small group of extremely wealthy people to fund a large public program. Voters, rather than the taxpayers themselves, will decide whether it proceeds.

Proposition 40 targets billionaires because it is designed as a wealth tax on a very small, exceptionally wealthy group. The measure covers roughly 250 Californians instead of applying broadly across the state’s population. Its stated purpose is to raise money quickly for threatened health coverage.

The key mechanism is concentration. A 5% levy on total professional and personal wealth can produce a large projected sum when applied to billionaires’ holdings. Supporters estimate $100 billion, enough to make the tax relevant to coverage for 3.5 million Californians. The article does not give individual wealth figures or a separate justification.

This design also makes the campaign politically focused. The SEIU-UHW union backed the proposal and collected 875,000 signatures to place it on the ballot. If voters approve it, the burden would fall on the targeted billionaires, not the population as a whole. If they reject it, the article gives no replacement plan.

Gabriel Zucman is a 39-year-old French-American economist. He is one of two University of California, Berkeley professors whose work directly inspired Proposition 40. The other is Emmanuel Saez, described as Zucman’s mentor and friend.

Zucman became personally involved in the campaign. During a flight from Europe to San Francisco, he spent all 11 hours refining a “manifesto against the international oligarchy.” After arriving, he attended conferences, meetings, interviews, and filming sessions designed to promote the campaign on social media.

His role shows how the proposal connects academic work with electoral politics. He had also traveled to Budapest to help Hungary’s new government with a wealth-tax project. The article does not explain the precise findings of his research. It does show him campaigning energetically for Proposition 40 alongside communications staff and union-backed organizers.

The projected $100 billion would be used to protect health coverage for 3.5 million Californians. The article presents this as the proposal’s central public purpose. It does not name the specific health program or describe how the money would be distributed.

The immediate threat comes from cuts imposed by the One Big Beautiful Bill. President Donald Trump signed that bill on July 4, 2025. Proposition 40’s backers therefore connect the proposed wealth tax directly to preventing or limiting the coverage losses they expect from those cuts.

The result would depend on both voter approval and the projected revenue being collected. The article describes the $100 billion as an estimate, not money already raised. It also gives no timetable, implementation details, or guarantee that every threatened person would retain coverage. Its stated goal, however, is clear: preserve health coverage for 3.5 million Californians.

The article does not identify what California would do if voters reject Proposition 40. It only describes the proposed wealth tax and its intended use: protecting health coverage for 3.5 million Californians facing cuts. Any replacement would therefore require a different funding decision.

Possible approaches, based on established public-finance practice rather than this article, include raising income, sales, property, or corporate taxes. California could also redirect existing spending, borrow money, seek federal support, or reduce the scale of coverage protections. Each option would use a different group of payers or create a different budget trade-off.

The choice would involve more than finding $100 billion on paper. Officials would need to consider how dependable the revenue is, how quickly it arrives, and who bears the cost. The article provides no evidence that any alternative has been proposed, costed, or prepared for a vote.

An income tax applies to money received during a period, such as wages, business earnings, or investment returns. A wealth tax applies to a person’s accumulated net worth: the value of assets minus debts. Proposition 40 is described as taxing total wealth, including professional and personal holdings, rather than yearly income.

The difference matters because wealth can exist without producing much taxable income. A person may own businesses, property, shares, or other assets whose value rises without being sold. A wealth tax would need officials to identify those assets, value them regularly, and determine which debts reduce the taxable amount.

Administration can therefore be difficult. Private companies, artwork, property, and complex investments may lack a simple market price. Assets can also be held across borders or through legal structures. These are general features of wealth taxation; the article itself does not discuss administrative rules or implementation problems for Proposition 40.