A small group of traders dominates volume on major election prediction platforms

Concentration behind the election odds

Election betting markets face questions about how much confidence readers should place in their prices, according to Athlitical’s reporting on an Anti-Corruption Data Collective analysis. The findings point to concentrated trading and markets whose prices can shift with very little money.

The analysis covered 21,811 midterm markets. It found more than 220 million dollars wagered on 2026 congressional races through September 30—a substantial total that sits alongside evidence of thin trading in individual markets.

Volume does not guarantee depth

On Polymarket, the top 1 percent of wallets accounted for 70 percent of congressional volume, according to the analysis reported by Athlitical. That concentration makes it important to distinguish trading activity from broad participation: a large volume figure does not necessarily represent a wide range of independent views.

The analysis also found that more than half of markets could be moved five cents for less than a dollar. For readers following election odds, that finding raises a separate concern about whether a price change reflects a meaningful shift in expectations or simply limited market depth.

What it means for prediction markets

• Volume and depth are different measures. More than 220 million dollars in aggregate wagering does not establish that individual congressional markets can absorb trades without significant price changes.
• Wallet concentration complicates interpretation. With the top 1 percent of Polymarket wallets generating 70 percent of congressional volume, prices should not automatically be read as a broad consensus.
• Small price moves need context. The finding that more than half of markets could move five cents for less than a dollar cautions against treating every change in election odds as a strong signal.