USA vs Belgium: two goals two minutes apart, priced in opposite order

Most of the time, when Kalshi and Polymarket price the same live game, a goal reaches both order books inside the same minute. The Round of 16 match between the USA and Belgium on 6 July, at Lumen Field in Seattle, is the exception. Two goals landed two minutes apart, and each book led on a different one.

Belgium had led 1-0 since Charles De Ketelaere's goal in the 8th minute, and Belgium's win price had settled at 60 percent on both venues by the half-hour mark. In the 31st minute Malik Tillman equalized for the USA. Two minutes later De Ketelaere scored again to put Belgium back in front. Belgium went on to win 4-1.

Here is what the two books did with those two goals, in one-minute snapshots of Belgium's win price.

Kalshi reacted to the equalizer first. Its Belgium price fell from 0.60 to 0.37 in the minute the goal went in, a 23-point drop. Polymarket did not move in that same minute; it was still sitting at 0.60 while Kalshi had already priced in a tied match. By the next minute Polymarket caught down to 0.35, in line with Kalshi's 0.37, and the two books briefly agreed again.

That agreement lasted one minute. De Ketelaere's goal landed in the 33rd, and this time Polymarket moved first, jumping from 0.35 to 0.62. Kalshi held at 0.35 for that same minute, running the same one-minute lag it had just watched Polymarket run, now in the other direction and on the other book. By the 34th minute Kalshi had caught up to 0.62, a point off Polymarket's 0.61. The next minute put them at 0.63 and 0.64, and by the 36th both books read 0.63.

The market prices three outcomes: Belgium to win, the USA to win, or a draw. A clean arbitrage here means holding all three, one leg per outcome, split across both books. Our feed caught two of those three-leg trades in this window. From 00:33:21 to 00:34:14 UTC, Belgium on Kalshi plus the USA and the draw on Polymarket together cost about 4.78 percent less than the dollar they would pay out, sized to $75 by the thinnest of the three order books. From 00:34:15 to 00:36:44 UTC, as Kalshi caught up to Polymarket's second move, that edge widened to 18.99 percent, sized to $871. Both closed the same way the price gap did, on convergence, not on the game ending.

One caveat our matcher carries on this market: Kalshi states a rule for pricing a cancelled game fairly, and Polymarket does not say what it does in that case. The game was played to completion, so it never mattered here, but it is why this pairing needed a human read rather than shipping straight through the automated feed.

The matched feed and the price history behind this post are on REST, free to read on any plan. Real-time push, where each price update reaches you as it happens, is on Basic and Pro. The Quickstart pulls your first feed on a free key.