Do Prediction Markets Move Before the News? Unusual Price Moves Before Results

By Arthur Angelo, PredictionScout Research · Updated Oct 11, 2026, 9:48 AM ET

Key findings

• Most surprises stayed surprises until the end. Of 761 markets where the eventual winner cost under 50¢ a day before the outcome was clear, 522 (68.6%) had become the favorite by one hour before. The rest were still underdogs right up to the last hour.
• Sharp late moves are uncommon. We flag 356 markets where the winner was at 35¢ or less a day out and rose at least 30 points by an hour before the decision.
• Big late moves usually point the right way. Across all 10,498 markets, the price moved 30+ points toward the eventual outcome in the final day 1,035 times and 30+ points away from it 52 times (95% toward the outcome).
• Scheduled announcements (economic data releases and Fed decisions, where the release time is fixed in advance): 25 of 1,289 markets moved 30+ points toward the outcome in the final day, and 10 met our flag. For unscheduled news the counts were 1,010 of 9,209 and 346.
• By exchange: 44 flagged on Kalshi (of 131 underdog winners) and 312 on Polymarket (of 630). The exchanges list different markets, so this is not a like-for-like comparison.

How much did underdog winners move in the final day?

The largest late moves

Markets that resolved YES where the YES price was 35¢ or less 24 hours before the outcome became clear and had risen at least 30 points one hour before. “Decision time” is our estimate from prices (see methodology), not the time of an official announcement. We have not checked each case against news reports; many will turn out to be the market reacting to public reporting that came out before the formal result.

Download the data

All checked markets (CSV)

Every market in this study with the eventual outcome’s price 24 hours, 6 hours and 1 hour before the decision time, the move, whether it met our flag, scheduled or unscheduled, exchange, category, volume and link. No trader-level data is included. Free to reuse under CC BY 4.0.

Methodology

• Markets. From the settled-market sample in our accuracy scorecard (Kalshi: at least 50,000 contracts traded; Polymarket: at least $50,000 volume; closed since January 1, 2025). We keep only outcomes revealed by an announcement or decision, such as appointments, legal rulings, company news, awards, economic data and Fed decisions.
• What we leave out, and why. Sports, crypto and stock prices, commodities, weather, election-night vote counts, “what will they say” markets, and markets settled by a public tracker or broadcast (social-media post counts, polling averages, streaming and music charts, review scores, app-store rankings, who attends a televised event, and live-broadcast award shows and contests). In those, the outcome unfolds in public (a game, a price chart, a vote count, a live speech), so a late price move is just the market watching.
• Decision time. The first hour after which the eventual outcome’s price stayed at 99¢ or more until the market closed, or the close if that never happened. For scheduled data releases on Kalshi, markets close just before the release, so this is the last price before the number came out.
• The flag. The market resolved YES; its YES price was 35¢ or less 24 hours before the decision time; and it was at least 30 points higher one hour before. We only flag YES outcomes because a falling YES price near a deadline (“will X happen by Friday?”) is usually just time running out.
• Prices. Kalshi: midpoint of the hourly bid and ask when the spread is 10¢ or less, otherwise the last trade. Polymarket: hourly price history from its public API.
• No trader data. We do not look at accounts or wallets and make no claim about who traded or why.

What a flag does and does not mean

• A flag means the price moved a lot, early. It is not evidence of insider trading or any other misconduct.
• Common innocent explanations: news or credible reports published before the formal announcement; a decision that became predictable from public signals (a scheduled vote, a leaked agenda, a court calendar); one large trader with a strong opinion in a thin market; and plain luck.
• Our decision time is estimated from prices. If public news broke a few hours before the price locked in at 99¢, the move we measure may be a reaction to that news, not a move ahead of it.
• Both exchanges prohibit trading on material non-public information in their rules, and the CFTC can investigate. Questions about specific trades belong with the exchanges and regulators, who can see account-level data that we cannot.

Data sources: prices and volumes come from the public APIs of Kalshi and Polymarket. All trademarks belong to their owners. PredictionScout is independent and not affiliated with any exchange. Nothing here is investment, betting, or legal advice.

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