California billionaire tax slides: Prop 40 passage down 8 points to about 25%

California’s billionaire-tax proposal, Prop 40, is trading at roughly a one-in-four chance of passage, according to DeFi Rate. Kalshi’s implied probability fell 8 percentage points over the past week to 26%, extending the decline described in the Oct. 13 report.

Prices point to a difficult path

The summary of DeFi Rate’s observations at 12:26–12:28 PM ET on Oct. 13 puts passage contracts at 26¢ on Kalshi and 25¢ on Polymarket, with $15K in combined 24-hour volume. The supplied source excerpt lists Kalshi at 26% and Polymarket at 24%, a slightly different Polymarket reading.

DeFi Rate’s roughly one-in-four assessment averages the 26% Kalshi and 24% Polymarket figures. At Polymarket’s listed 24¢ asking price, the outlet calculates that a $100 purchase would pay $416 if the outcome is correct, before fees. That figure is a payout, not net profit.

The report’s headline contrasts the falling market odds with polls showing Yes ahead. However, the supplied material contains no poll dates, margins or methodology, limiting any assessment of why the polling signal and market prices differ.

What it means for prediction markets

• The weekly move is clear: Kalshi’s passage probability dropped 8 percentage points to 26%; the supplied material does not identify a cause.
• Snapshot precision matters: Polymarket is listed at 25¢ in the observation summary and 24¢ in the source excerpt. Both put passage near one in four, but they are distinct price readings.
• The polling comparison remains incomplete: A Yes lead in polls and low passage odds present contrasting signals, but the available polling details are insufficient to explain the gap.
• Volume provides context, not conviction: The reported $15K in combined 24-hour volume does not, by itself, establish how broadly held the market’s assessment is.