Polymarket midterm volume hits 133 million dollars but 1% of wallets hold 68% of bets

A single data point from the Anti-Corruption Data Collective landed this week and it cuts against the narrative that prediction markets have become a reliable barometer of public opinion. By August 10, traders had placed at least $133 million across Polymarket markets tied to 2026 House and Senate races — more than the entire $92.4 million staked across comparable congressional markets during the whole of 2024.

The concentration figures are harder to dismiss. The top 1% of wallets on Polymarket Global account for 68% of congressional volume. Ten wallets alone produced 17% of total trades, spread across contracts touching 426 of the 470 seats on the ballot.

The ACDC analysis covered 7,466 markets across Kalshi, Polymarket, and Polymarket US. Eighty percent of Polymarket's congressional contracts have fewer than 100 participating wallets. In a market that thin, a single funded order can shift the displayed probability without any change in the underlying race.

Four markets — Texas, Maine, and Michigan Senate contracts plus Kentucky's 4th Congressional District — account for 67% of state-level volume, leaving hundreds of granular contracts where the displayed price reflects a handful of traders whose information and motives are opaque to everyone else.

About the analyst

Sebastian Montague

Prediction Markets Trader

Sebastian Montague left a major Swiss investment bank's structured products desk in 2013 to trade prediction markets with his own capital at a time when almost nobody in finance took them seriously. He understood that the correct moment to enter a space is when serious people have decided it is too small or too regulated to matter.