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Updated September 25, 2026 · facts checked against the dated sources listed below
Traders buying and selling shares move Polymarket prices, so anything that changes what they expect, or how much money stands behind an order, can move them: news, polls and data releases, large traders, thin order books, the exact wording of the rules and the passing of time. A big move is not always new information; in a thin market a single order can shift the displayed price.
Polymarket's documentation says it does not set prices: they come from users trading with each other on a central limit order book. The price you see is the midpoint between the best bid and the best ask, unless the gap between them is wider than 10 cents, in which case Polymarket shows the last traded price. A buyer pays the ask and a seller receives the bid, so the displayed number is not always a price you can trade at.
To keep markets active and balanced, Polymarket pays daily liquidity rewards to traders whose resting limit orders sit close to the midpoint; the closer the order, the more it earns.
See also: How to read a Polymarket order book · Midpoint price · Bid-ask spread
Surprise news moves prices fastest. Polymarket's market on whether President Biden would drop out stood at about 20% before the June 27, 2024 debate and reached nearly 80% on July 3 after a New York Times report, CoinDesk reported. After the July 13, 2024 assassination attempt, Donald Trump's shares in the presidential winner market rose from about 60 cents to 70 cents that evening, and within hours of Biden's withdrawal on July 21, Kamala Harris was at 82% to win the Democratic nomination.
Economic data works the same way. The August 2026 consumer price index came out at 8:30 a.m. Eastern on September 11, 2026, with core prices up 0.3% for the month against 0.2% expected. Polymarket's price for a 25 basis point September Fed hike went from 59.5 cents at 12:29 UTC to 79.5 cents at 12:31 UTC, according to its price history, and the Fed raised rates by 25 basis points on September 16.
See also: Fed rate odds for every upcoming FOMC meeting
Polls move election markets when they surprise. The final Des Moines Register/Selzer Iowa Poll, released on November 2, 2024, showed Harris ahead of Trump 47% to 44% in Iowa. Within five minutes, from 23:00 UTC that evening, Polymarket's price for a Democratic win in Iowa jumped from 8.5 cents to 18 cents. Trump's national odds on Polymarket slipped from 65% on October 27 to 56% by the evening of November 3. The Iowa market later resolved No: one poll can move a price a long way, right or wrong.
See also: Polymarket vs polls
Big orders move thin books and can move deep ones too. In October 2024, Polymarket said four accounts holding about $28.6 million of pro-Trump positions belonged to one French trader, and that its review with outside experts found no sign of manipulation. An on-chain study later estimated that moving Polymarket's Trump price by five points in October 2024 cost about $9.1 million, with money coming in on both sides.
Some moves come from people who may know more than the market. About 11 hours before the October 10, 2025 Nobel Peace Prize announcement, María Corina Machado's odds on Polymarket jumped from about 1% to over 70%, and Nobel organizers began looking into possible insider trading. In April 2026 the US Justice Department charged a soldier with using classified information about the January 3, 2026 operation that captured Nicolás Maduro to bet about $33,000 on Polymarket; he is accused of making about $409,881. In September 2026 the CFTC warned that markets on what one person will say or do carry a heightened risk of manipulation.
See also: Whale · Polymarket biggest movers
The thinner the order book, the less money it takes to move the price, so check the spread and depth before trusting a sharp move. Volume can mislead too: Columbia University researchers estimated in November 2025 that wash trading, in which traders buy from and sell to themselves, averaged about 25% of Polymarket's volume over three years and peaked near 60% in December 2024.
See also: Liquidity · Trading volume
The rules decide what counts, so a clarification or dispute can move a price as much as news. After US forces captured Maduro on January 3, 2026, Polymarket's contract on a US invasion of Venezuela by January 31 jumped from 2.5 cents to about 60 cents within hours, then sank to about 5 cents by January 5. Polymarket said the raid did not meet its definition of an invasion, and the market resolved No.
In July 2025, the Yes price in a market on whether Volodymyr Zelenskyy would wear a suit before July fell from 19 cents to 4 cents as an initial Yes result was disputed; the market resolved No.
See also: How Polymarket markets resolve · What happens when a market is canceled
In “by date” markets, time alone pushes the Yes price down while nothing happens, because each day without the event leaves less time for it. In Polymarket's ladder on a US invasion of Venezuela, the contract for “by December 31, 2025” slid from about 4 cents on December 17 to 0.4 cents on December 30, while the contract for “by March 31, 2026” held around 14 cents over the same days, according to Polymarket's price history.
Prices also sharpen as the close nears: in our accuracy study, prices a day before the close were more accurate than prices a week or a month out. When a price jumps, ask what changed: news, a poll or data release, one large order in a thin book, or how the rules are read. This is educational information, not financial advice.
See also: How “by date” markets work · How accurate is Polymarket?
Usually because of news, a poll or data release, or a large order hitting a thin order book. If the spread is wider than 10 cents, the displayed price is the last trade, so a single trade can look like a big move.
In thin markets, yes. Deep markets take much more money: one study estimated that moving Polymarket's Trump price by five points in October 2024 cost about $9.1 million.
Not all of it. Columbia University researchers estimated that wash trading averaged about 25% of Polymarket's volume over three years, so treat volume as a rough guide to activity.
Each day that passes without the event leaves less time for it to happen, so the Yes price tends to drift down unless news raises the odds.
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