California's Billionaire Tax Draws Warning from French Economic Troubles

California's proposed "billionaire tax," formally known as Proposition 40, is drawing attention for its potential economic impacts, with critics pointing to France's experience with similar wealth taxes and expansive social spending as a cautionary tale. The one-time 5% tax targets California residents with assets exceeding $1 billion.

The proposition's intellectual roots trace back to French economists Emmanuel Saez and Gabriel Zucman, both affiliated with UC Berkeley, and Thomas Piketty, author of "Capital in the Twenty-First Century." Their work has influenced wealth tax proposals in the United States, including those by Senators Bernie Sanders and Elizabeth Warren.

However, opponents argue that California should heed France's economic trajectory. Recent increases in French bond yields have been attributed, in part, to fiscal challenges stemming from sluggish economic growth, high taxes, and extensive regulation. In the previous year, French public spending reached 57.3% of its gross domestic product, with a deficit of 5.1% and public debt climbing to 119% of national output by June.

France's pension system, a significant component of its public spending, accounted for €422 billion, or 14.1% of GDP, in 2025. Despite efforts to address these financial pressures, including raising the retirement age, these reforms have faced political and social challenges.

Historical Precedents and Economic Concerns

France has a history with wealth taxes. A wealth tax implemented in 1982 was abolished in 1986 after wealthy taxpayers relocated. A subsequent wealth tax, reinstated in 1989, was significantly narrowed in 2018 to apply only to real estate, not financial assets.

Economists like Josh Rauh of the Hoover Institution have raised concerns about the potential revenue generation of California's Proposition 40. A study by Rauh and colleagues estimated the tax might collect around $40 billion, substantially less than the $100 billion projected by proponents. This shortfall is partly attributed to the anticipation that wealthy individuals may leave the state to avoid the tax. One analysis suggests that the out-migration of billionaires could lead to a long-term loss of $24.7 billion in future income tax revenue for California.

Beyond direct tax revenue, critics argue that such policies can deter investment. Billionaires, when deciding where to allocate their capital, may consider the possibility of future taxes, even those initially framed as one-time measures. Supporters of the tax, however, maintain that it would generate significant revenue, with a substantial portion earmarked for healthcare, an appealing prospect for voters concerned about essential services. Yet, the argument persists that the negative economic consequences, as potentially demonstrated by France's fiscal situation and past tax policies, could outweigh the intended benefits.