If you have less than $1 billion in wealth, this tax does NOT apply to you.
Explore the research on California’s proposed billionaire tax. Read the reports, find answers to your questions, and follow the original sources.
14Full reports to read online
128Original pages of analysis
10Named research authors
Open a question for a short guide, then go straight to the report passage.
No. If you have less than $1 billion in wealth, the tax does NOT apply to you.
There is no way for the legislature to change Prop 40 to make it apply to anyone else who isn’t a billionaire.
The authors describe new money for healthcare, schools, and food assistance. They explain how federal funding changes could affect insurance coverage, hospitals, and other providers.
The expert report estimates about $100 billion over 2027–2031, using its stated wealth data and allowance for avoidance. The report also explains how asset values could change the result.
The response report separates announced moves from changes in tax residence. It challenges the competing model’s assumptions about future income-tax losses and acknowledges limits in public residency data.
The reports distinguish a company from an owner’s stake. The valuation report explains public-company shares, private-business formulas, and appraisals. The expert report separately discusses payment options.
The legal report sets out the drafters’ reasoning under state and federal law. Thirteen sections address objections and link to cited court decisions. It is legal analysis, not a court decision about Prop 40.
Fourteen reports, with full text, linked sources, and source-connected metadata.
Brian Galle, David Gamage, Emmanuel Saez, Darien Shanske
The drafters explain the tax’s design, their revenue estimate, payment options, and constitutional reasoning.
Brian Galle, David Gamage, Emmanuel Saez, Darien Shanske
A response to the March 4, 2026 fiscal study, focusing on recurring-tax assumptions, residency, and estimated income-tax losses.
Brian Galle, David Gamage, Darien Shanske
The drafters respond to constitutional objections, including takings, retroactivity, interstate commerce, and the right to travel.
Brian Galle, David Gamage, Emmanuel Saez, Darien Shanske
An explanation of public-company shares, private-business valuation presumptions, and certified appraisals.
Emmanuel Saez, Gabriel Zucman
Emmanuel Saez and Gabriel Zucman discuss wealth growth, income taxes, revenue, and the design of the proposed tax.
James Paci, Shawn Blosser, Matthew Newman
Charles W. Rhodes, Adam B. Thimmesch
SEIU-UHW Research Department
HR1 and the Federal Subsidy Cliff Are Driving the Spike — and Medi-Cal Cuts Push the Bill Onto Everyone.
Spillover Effects of HR1 Medicaid Cuts and Hospital Closures
SEIU-UHW Research Department
By replacing Bay Area tech workers with AI and misclassifying gig workers across the state, California’s tech billionaires are pushing Californians out of good jobs.
How the federal budget law cuts health care and food assistance, causing ripple effects that devastate public safety, energy costs, mental health, housing, and consumer affordability, all to fund a historic immigration enforcement surge — and what it means for California
SEIU-UHW Research Department
Billionaires pay low taxes compared to working Californians by keeping their reported income low while their wealth – most of which is unrealized and never taxed – has more than doubled in the last three years alone.
Issue Brief: Anthropic and OpenAI Initial Public Offerings are projected to generate enormous wealth for tech sector billionaires in California
No matching report. Try “healthcare,” “moving,” “valuation,” or an author’s name.
The reports present the named authors’ research and arguments. The original text retains each edition’s figures, qualifications, and source notes. The reading guides are separate summaries, not changes to the reports.
Explore the data, legal scholarship, and methods cited in the library.
Jasper Boll, Emmanuel Saez, and Gabriel Zucman
Working-paper data and methods for estimating California billionaire wealth and tax revenue.
Brian Galle, David Gamage, and Darien Shanske
A review of state taxation, migration research, and the distinction between reported moves and changes in tax residence.
Read the sourceBrian Galle, David Gamage, and Darien Shanske
Research on valuing difficult-to-sell assets and structuring tax payments. Background scholarship, not the text of Prop 40.
Read the sourceAkcan Balkir, Emmanuel Saez, Danny Yagan, and Gabriel Zucman
The administrative-data research cited in the reports’ discussions of U.S. billionaire taxation.
Brian Galle in conversation with Gwyneth Shaw
A Berkeley Law interview with a full transcript, covering federal proposals and the California initiative.
Read the sourceRead the legal text and the official fiscal assessment alongside the research.
California Attorney General — filed initiative text
The proposed constitutional and statutory language, including eligibility, valuation, spending, and payment rules.
California Legislative Analyst’s Office
The official fiscal assessment of initiative 25-0024A1, published separately from the authors’ reports.
Read the source