Golf 2026 — the Irish Open and the durable boards

The Amgen Irish Open is the largest golf book on any exchange: $606,984 on Kalshi across 144 players. Polymarket lists the same tournament—both an outright winner board and a top-five board—and has turned on either.

The Kalshi board sums to 114.4%, which is tight for a 144-name field, and the money is concentrated where the price is. Rory McIlroy leads at 12.5% on $37,269; Jon Rahm is 8.6% on $25,533; Robert MacIntyre is 4.3% on $15,449 and Joaquin Niemann 4.5% on $11,359. For once on these pages the flow follows the favourites rather than the tail—MacIntyre is the only name in the top four taking more money than his price implies.

The tournament runs to September 13, so the winner board has four days left and the Omega European Masters top-five and top-ten boards that sat here yesterday have both settled and been replaced by the Irish Open's own cross-exchange mirrors.

Underneath, the durable golf contracts: the 2027 majors board, the Presidents Cup, and the two career markets—Scheffler's career slam, running to 2028, and whether Tiger Woods plays a PGA Tour event this year. Those are the ones that survive from refresh to refresh; everything above them turns over weekly.

The Irish Open on both exchanges that list it. Kalshi: 144 players, 114.4% total, $606,984 today, McIlroy 12.5%. Polymarket: the same field, and no trades at all. A listed-but-untraded board is not a second price—it is an empty shell, and the spread this workspace usually reads simply does not exist on this tournament.

The two names carrying the board. McIlroy is 12.5% and has taken $37,269; Rahm is 8.6% on $25,533. Between them they are 21% of the field's probability and 10% of a 144-player board's daily volume—the concentration you would expect and rarely get on a field this wide.

Polymarket's Irish Open winner and top-five boards, both listed with the full field and both showing zero volume through the tournament's opening days. Kalshi's equivalent turned $606,984 in the same window. Worth watching whether either fills before Sunday—if not, the Irish Open is a single-venue market in practice.

The two names carrying the Irish Open. McIlroy at 12.5% has taken $37,269 and Rahm at 8.6% $25,533—between them a fifth of the board's probability and a tenth of its daily volume. Both are two-sided and both have moved on today's play; almost nothing else in a 144-player field has.

The contracts that outlive any one tournament. Scheffler's career grand slam runs to 2028 and the Tiger Woods appearance market to the end of this season; the 2027 majors board and the Presidents Cup frame the calendar around them. These are the golf markets with real horizon; the weekly tour boards above them settle and roll every seven days.

The Irish Open settles September 13 and the Presidents Cup September 27. Between them they are the whole of the live golf calendar on these boards.

Polymarket's two Irish Open boards have taken no money at all. They are listed with full fields and zero flow while Kalshi turns $606,984 on the same tournament. If they stay empty through Sunday, golf is effectively a single-venue market and the cross-exchange read on this page disappears.

114.4% across 144 players is the tightest wide-field board this workspace tracks. Compare it with the NASCAR title board at 121.5% across 35 drivers—four times the field, seven points less overround.

The durable contracts are where to look between tournaments—Scheffler's career slam to 2028, the 2027 majors board, and the Tiger Woods appearance market. They do not roll weekly and they are the only golf markets here with a horizon longer than four days.