What Prop 40 would do

California's Proposition 40, on the November 3 ballot, would impose a one-time five percent wealth tax on state residents with net worth above one billion dollars.

How many billionaires

An estimated two hundred billionaire individuals live in California, based on tracking of Forbes data, according to economics professor Alan Auerbach at Berkeley.

Revenue projections

Proponents say Proposition 40 could raise roughly one hundred billion dollars in new tax revenue, accounting for ten percent of tax avoidance and evasion.

Where the money goes

The vast majority of tax revenue would fund state healthcare programs to offset healthcare cuts from President Trump's One Big Beautiful Bill Act signed into law last year.

Early polling showed support

In March, polling showed fifty-two percent support for Proposition 40 with only thirty-three percent opposed, a nineteen percent margin for the yes vote.

Support has narrowed

By September, a University of California Berkeley poll found forty-five percent would vote yes and forty-two percent would vote no, shrinking the yes edge from seven percent to three percent.

Prediction markets expect defeat

While yes continues to lead in polls, prediction markets Kalshi and Polymarket have odds of passage currently at under thirty percent.

Partisan divide

Democrats support Proposition 40 by more than three to one, while Republicans are opposed nearly eight to one, according to polling data.

Newsom opposes the measure

Governor Gavin Newsom has argued that billionaires can and do move to states with lower taxes, weakening California's long-term tax base.

“Wealth is movable, and it shops for the state with the lowest taxes.”

Both governor candidates oppose it

Democratic candidate Xavier Becerra and Republican candidate Steve Hilton both said they will vote no on Proposition 40, citing concerns about driving tax revenue out of the state.

Billionaires funding opposition

Google co-founder Sergey Brin is among billionaires pouring money into defeating the measure, spending forty times what he put into politics in the previous two decades.

Opposition spending

Building a Better California, whose top donors include Sergey Brin, has spent roughly one hundred eighteen million dollars on the campaign, with billionaire-aligned groups spending an estimated one million dollars per day.

Zuckerberg threatens to leave

Meta founder and CEO Mark Zuckerberg recently threatened to leave California if the wealth tax passed, leading Meta's board to change its stock structure to insulate him from financial impact.

Nvidia CEO supports the tax

Nvidia CEO Jensen Huang, who would owe as much as eight billion dollars under the tax, told CBS Sunday Morning it would be a privilege to pay it.

“privilege”

Valuation challenges

Proposition 40 applies to liquid and illiquid assets including public equities, private business stakes, and venture capital holdings, raising concerns about how to value complex assets.

Competing ballot measures

Proposition 42 would bar retroactive taxes on retirement holdings and personal assets after January 1, 2026, potentially undercutting Proposition 40 if it receives more yes votes.

One-time or permanent tax

Critics worry the measure could become permanent despite being labeled one-time, citing precedent from Proposition 30 in 2012, which was extended beyond its original seven-year term.

Supporters confident in message

Healthcare unions backing Proposition 40 say they are seeing an enormous wave of voters who believe now is the moment to save healthcare for all Californians by taxing billionaires.