Mutually exclusive market

An event where exactly one outcome can win, such as a single election or a championship. The outcomes' fair probabilities sum to 100 percent, unlike multi-select events where several outcomes can occur.

The distinction drives how odds should be read. In a one-winner event the field summing to 104 cents means a 4 percent overround; in a multi-select event a field summing to 170 percent is normal and not a mispricing. Confusing the two is a classic error our odds boards guard against.