What prediction markets are saying about the chances of California passing a billionaire tax

Prediction Markets Gauge Prospects for California Wealth Tax Initiative

Prediction markets have adjusted their assessments following recent reports on a proposed California ballot measure that would impose a one-time tax on residents and certain trusts with net worth of at least $1 billion.

As of June 17, contracts on Kalshi and Polymarket placed the likelihood that the measure would qualify for the November ballot at just under 50 percent. Both platforms recorded sharp declines after Bloomberg and Politico reported that Gov. Gavin Newsom had directed staff to prevent the initiative from reaching voters. Prior to those reports, prices on both markets exceeded 80 percent, with Polymarket briefly reaching near 90 percent. The June 25 certification deadline remains the next procedural step.

Traders on the same platforms assigned lower probabilities to passage by voters. Kalshi contracts implied roughly a 19 percent chance of approval, while Polymarket contracts stood at 18 percent. Both markets price only the outcome of a simple-majority vote, assuming the measure first qualifies.

The initiative would apply a 5 percent rate to net worth at or above $1.1 billion for tax year 2026, with a phase-in range between $1 billion and $1.1 billion. It would cover California residents and certain trusts as of January 1, 2026. The measure’s retroactive application date has drawn attention because several high-net-worth individuals relocated assets from the state before signature gathering concluded.

The proposal has produced divisions among organizations that have previously aligned with California Democrats. The SEIU-UHW healthcare workers union has supported qualification, while affiliates of Planned Parenthood and the California Teachers Association have opposed it.

California currently has more residents with net worth above $1 billion than any other state. Qualification would not conclude the policy debate. “Building a Better California,” a political action committee, has received $129 million from ten donors to support competing ballot measures. Sergey Brin has contributed $82 million and Eric Schmidt roughly $3 million. One of the committee’s measures would prohibit new taxes on ownership or control of personal property and bar retroactive taxation. Under California rules, when two measures both receive a majority, the version with more votes prevails.

Separately, Ripple Labs and its executive chairman Chris Larsen each gave $5 million to “Golden State Promise,” which was formed to defeat the wealth-tax proposal. Investor Ron Conway contributed $100,000 to “Stop the Squeeze,” another opposition committee. In a March interview, Conway stated that preventing the measure from reaching the ballot required further action and that negotiation with the governor would be necessary if it advanced.

The two prediction-market platforms operate under different regulatory frameworks and participant pools, yet both have shown similar directional shifts since the initial reports on Newsom’s position. No additional public statements from the governor’s office on the certification process have been issued since the June 17 market levels were recorded.