What is the house edge?

The cut a bookie bakes into the odds so they win either way. Prediction markets skip it; play money really skips it.

Add up a sportsbook's implied percents for every outcome and you get about 105%. That extra 5% is the vig, the house's bite, hidden inside the odds.

Prediction markets are peer-to-peer, so the percents actually sum to 100. And on a play-money market there's no rake at all, because there's no money to rake.