The Google co-founder, and world’s fourth-richest person, has spent $102 million so far to put a stop to the one-time, five percent tax on the wealth of California billionaires, according to filings tallied by Bloomberg. California voters can have their say on Proposition 40 for free come November.

California's Prop 40 would impose a one-time 5% tax on the net worth of the state's billionaires.

Google co-founder Sergey Brin has donated over $100 million to oppose California's proposed billionaire tax, which could cost him an estimated $13.3 billion in payments.