About ProbCast
ProbCast checks whether a prediction-market price is backed by real trading. A 20-point move on $8K of liquidity is not the same evidence as a 2-point move on $300K, and a headline number is sometimes a single small trade. ProbCast scores every move it tracks for liquidity and trust, says whether it looks like a real repricing or noise, and grades the venues' past prices against what actually happened.
Who runs it
ProbCast is built and run by an independent developer. It is not affiliated with, paid by, or partnered with Polymarket, Kalshi, Manifold, or any other venue, and it takes no paid placements. It does not offer trading, take positions on behalf of readers, or earn anything from where readers trade. Questions, corrections and data requests go to [email protected] or @probcastco on X.
How the scores work
Every formula, weight and penalty is published on the methodology page. The short version: Trust = 0.7 × Liquidity + 0.3 × (100 − Movement), minus fixed penalties for thin books, wide spreads, stale prices, past deadlines and trading dominated by one account. A move is labelled Confirmed only when it actually moved (2+ points in 24h) on a real-money venue with solid liquidity and trust.
What it covers, and what it doesn't
ProbCast tracks a curated slice: the most-traded open markets on each venue plus markets readers search for, not every market that exists. Manifold is play money and is tagged as such everywhere. The coverage page lists exactly what is tracked, by venue and category, and the known gaps.
What a high trust score does and doesn't mean
A high trust score means the price was earned in a deep, active market. It does not mean the price is right. Whether these prices are accurate is a separate question, answered by the track record: resolved markets graded on what they showed 24 hours, 7 days and 30 days before they settled. Whether a high trust score predicts better accuracy is still being measured, and the result will be published there either way.
Caveats
Venue data can be delayed or wrong, and every market links to its venue so you can check the live book. ProbCast provides prediction-market data and analytics for informational purposes only. Not financial, trading, betting, investment, legal, or tax advice.