TheOVERROUND
Cross-venue scan · MLB · games

Every venue quotes prices that add up to more than 100%. That excess is the overround, the margin the house keeps. We strip it out of every quote, then show you what each venue actually believes. No affiliate link decides what appears on this page.

Games matched
priced on 2+ venues right now
Median disagreement
pts
across all matched games
Widest gap
pts
Games over 2 pts
where the venues genuinely differ

The Board

Every game currently priced on more than one venue, sorted by how much the venues disagree. Each dot is one venue's de-vigged probability for the favourite, with the margin removed so the numbers are comparable. The full 0–100% scale is shown; we don't crop the axis to make small gaps look dramatic.

Kalshi Polymarket Sportsbook consensus

Where the gaps actually live

The first thing the data says, and it isn't the flattering answer: the eye-catching disagreements are concentrated in books nobody is trading.

A big gap in a thin book is not an opportunity. It's an absence of opinion.

Which points somewhere more interesting than arbitrage. If deep markets converge, the question worth answering isn't who's mispriced. It's which venue moves first, and who turns out to be right. That's a scoreboard, and it's the thing we're building.

The Scoreboard

Every market we track gets scored when it resolves. Not "who felt confident", but Brier scores and calibration curves, published with the methodology and the raw data. Nobody in this industry keeps score on themselves. We're going to keep it on everyone, including us.

Kalshi
Brier score. Lower is better. Scoring begins once we have resolved markets on the books.
Polymarket
Same window, same events, same method. Every venue is scored on identical markets or not at all.
Sportsbook consensus
Median de-vigged closing price across the book panel. The line to beat.

The house edge got smaller and nobody told the customers

A sportsbook holds somewhere between four and six percent on a two-way market. An exchange holds a fraction of that, because an exchange isn't taking the other side. It's charging rent on the room. That difference has been true for a while. What's new is the volume that finally noticed.

The interesting part isn't that exchanges are cheaper. It's what happens to a price when the person quoting it has no position in the outcome…

Also this week

The liquidity mirage. Why the biggest disagreements on this site are usually the least useful ones, and what to look at instead.

Reading a settlement rule. Two venues, the same event, different definitions of what "happened" means. This is where the real money gets lost.

What we get paid for. Our disclosure page, in plain language, including the parts that are awkward.