California Billionaires: Wealth, Taxes, and Wealth Tax Revenue Estimates

This paper documents the wealth of California’s billionaires and the taxes they pay. California billionaires’ wealth exceeds $2 trillion today, the equivalent of 50% of California’s GDP. It has grown 144% from 2023 to 2025, fueled by the AI boom. Over the longer run, the real wealth of California’s billionaire class—the 0.0002% richest households—has been multiplied by 30 from 1982 to 2025, while average real family income in California has about doubled. California billionaires pay about 0.2% of their wealth in California income tax ($3.2 billion/year), representing 2.4% of total California income tax revenue on average over 2023-2025. Using Securities and Exchange Commission data from Alphabet, Meta, Oracle, and Nvidia since 2004, we estimate the trajectory of wealth, income, and taxes paid by the top 4 California billionaires—Page, Brin, Zuckerberg, Ellison (through 2020), and Huang (since 2021)—focusing on their business wealth. This group alone holds nearly $1 trillion in business wealth, almost half of total California billionaire wealth. For this group, wealth growth (+322% over 2023-2025) and low taxation (0.04% of wealth in annual California income tax) are more pronounced. The proposed one-off California billionaire tax of 5%, payable over 5 years, is both small relative to California billionaires’ wealth gains and large relative to the taxes they currently pay. We estimate that it could raise about $100 billion, with comparatively minor impacts on income tax revenue. Using empirical estimates of mobility responses to wealth taxation, we find that an annual wealth tax on California billionaires could raise substantial additional revenue even after accounting for income tax losses due to mobility.