The house always wins. Except here, apparently.
Anyone who has spent time around sportsbooks knows the industry's quiet rule: the odd user might win, but most end up down. Industry analyses estimate that only around 3-5% of sportsbook customers are profitable over the long run. Which means roughly 95% lose money over time. In Brazil the picture is the same: the best-known day trading study, run by researchers at FGV and USP using B3 data, followed 19,646 people who started trading index mini contracts between 2013 and 2015. Among those who stuck with it for more than 300 trading days, 97% lost money. And even among the few who won, almost all took home less than R$300 a day.
And when someone does win consistently? The house limits how much that person can stake or, in extreme cases, suspends the account outright. Betfair went further and invented the Premium Charge: a special surcharge that reached 60%, applied specifically to its most consistent winners, and which only disappeared in early 2025, replaced by the Expert Fee, capped at 40%. Read that again: winning is so rare that the exchange created a tax for it.
was the maximum surcharge Betfair applied to its most consistent winners until early 2025. Its successor, the Expert Fee, still charges up to 40%. Winning is so rare that they taxed it.
That is the baseline. Now, what we found in our own Traderline Polymarket data during the 2026 World Cup.
The numbers
Traderline Polymarket is, as the name suggests, our professional trading terminal for Polymarket. Every trade routed through us is attributed on-chain, which means our numbers are not survey responses or marketing estimates. Anyone can recompute them from public data. Between the World Cup opener on 11 June 2026 and the final on 19 July:
59% of every user who traded during the World Cup finished the tournament in profit. Every single one, including people who tried the product once. 313 wallets closed the period with positive P&L. At a sportsbook, that ratio shows up inverted, several times over.
The more they trade, the more they win.
Normally, frequency of play predicts losses: the house edge compounds against you. Here it was the opposite: the people who traded most were the ones who most often ended in profit.
The World Cup also pushed the machine to its limit. On 7 July, as the round of 16 closed out, there were 56,405 trades and $8.6 million traded in 24 hours, the busiest day of the entire tournament.
Made by the World Cup's biggest winner on Traderline Polymarket: a wallet born with us mid-tournament, whose entire Polymarket history starts on 19 June, the day of its first trade on the terminal. From debut to the day of the final, that works out to roughly $6,400 a day.
Why prediction markets break the rule
A prediction market like Polymarket is a real order book. There is no house. Prices are set by traders. And nobody bans you for winning. In a prediction market, consistent winners are not a threat to the operator. They are the liquidity that makes the market work.
Everything is verifiable
There is one more structural difference worth highlighting, because it protects you even on your worst day: the entire system is non-custodial. Anywhere else, your balance is a number in the company's private database, one the operator can freeze, cap or dispute, and whose books no outsider will ever see. On Polymarket, your funds sit in your own wallet, your positions are tokens you hold, and every trade settles on-chain. And that matters even more if you use a white label solution: when you do not fully trust whoever holds the money, a non-custodial system is far safer.
It is also why we can publish an article like this one. Every number here covers the exact 2026 World Cup period, 11 June to 19 July (UTC), and comes from full sweeps of Polymarket's public APIs, verified across independent passes and checked wallet by wallet. The count follows Polymarket's builder convention: each attributed order counts once and, when both sides of a match go through the terminal, both count. Every trade behind these numbers can be audited by anyone with a laptop, including you.
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