"De-vigging, defined"

De-vigging removes the vig from a set of odds, so the implied probabilities sum back to exactly 100%.

The simplest method — proportional normalisation — divides each outcome's implied probability by the market total. If a market implies 55% and 50% (105% together), the de-vigged fair probabilities are 55 / 105 = 52.4% and 50 / 105 = 47.6%.

What remains is the market's genuine estimate, stripped of margin, and therefore directly comparable against your own model or against another market.

Doing this across a whole schedule is what a derived market line automates: de-vig each contributing source, then take the median across them, so no single stale or wide-margin source can skew the consensus.

See the vig explained: how de-vigging finds fair odds for the arithmetic and its limits.