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No-vig / de-vig
The price a book posts includes its margin (the vig). De-vigging removes that margin proportionally so the probabilities sum to 100 percent, leaving the fair number underneath. This is the math the whole honest-edge story rests on: your read only beats the book if it beats the fair price, not the posted one.
Book hold·
Overround·
Fair A·
Fair B·
qᵢ = raw implied prob · Overround M = Σ qᵢ · Hold = (M − 1)/M · Fair pᵢ = qᵢ / M
Market-neutral utility. It computes numbers you supply, it does not predict outcomes or guarantee profit. Compare lines across books and make the call yourself. 21+ · research, not advice.