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How Devigging Works

What it is

Devigging means stripping the bookmaker's margin out of a price so you can compare books apples-to-apples. Without devigging, every book looks like it has the same favorite at the same probability, which is not true. With devigging, you can see what each book actually thinks the fair probability is.

When to use it

Whenever you compare prices across books.
Whenever you want to estimate fair value before placing a bet.
Whenever you are evaluating an edge claim. Devigged numbers are the only honest comparison.

How to read it

The basic idea

Take a market with two sides priced at -110 / -110. The implied probabilities are 52.4% and 52.4%, summing to 104.8%. The extra 4.8% is the book's hold. To devig, scale both sides so they sum to 100%:

side_a_devig = 0.524 / 1.048 = 50.0%
side_b_devig = 0.524 / 1.048 = 50.0%

That is multiplicative devigging, the simplest method. There are also additive and power methods, each with slightly different assumptions. We use multiplicative as default; for two-way markets the differences are small.

Single-book vs consensus

Single-book devig tells you what one book thinks. If Pinnacle is the only book quoting, that is your best single-source fair value.

Consensus devig averages multiple sharp books, weighted by their historical calibration. This smooths out idiosyncratic errors and is what powers our v4 enrichment.

Our weights

The v4 consensus uses fixed sharp-book weights, recalibrated quarterly:

Book	Weight	Why
Pinnacle	45%	Lowest vig, highest limits, longest track record. The market.
LowVig + Circa	30% (combined)	Sharp offshore (LowVig) and sharp Vegas (Circa). Strong cross-check for Pinnacle.
BetOnlineAG	25%	Takes sharper action than most US books, useful when Pinnacle is missing.

Weights apply only when all three are quoting. When some are missing, the remaining books are renormalized.

Worked example

NBA total 220.5

Pinnacle:     Over -105 / Under -105     hold 4.7%   devig: 51.2% / 48.8%
LowVig:       Over -108 / Under -102     hold 4.8%   devig: 51.9% / 48.1%
Circa:        Over -110 / Under -110     hold 4.5%   devig: 50.0% / 50.0%
BetOnlineAG:  Over -107 / Under -103     hold 4.5%   devig: 51.5% / 48.5%

Weighted blended (v4_full):
  Pinnacle  45% * 51.2 = 23.04
  LowVig    15% * 51.9 =  7.79
  Circa     15% * 50.0 =  7.50
  BetOAG    25% * 51.5 = 12.88
  Sum:                  51.21%

v4 fair: Over 51.2% / Under 48.8%
v4 fair odds: Over -105 / Under +105

Now you can grade a soft book quoting Over -100 (50.0%) -> +1.2% edge.

Common mistakes

Devigging on a one-sided market. If only one side has a price, you cannot devig with one number. Use a multi-book consensus.
Treating multiplicative as universal. For three-way markets (soccer 1X2), use power or additive devigging.
Devigging soft-book prices and using them as fair value. Soft books are systematically biased. Always use sharp books for the anchor.
Forgetting that vig is sport-specific. Soccer markets have lower vig than NHL markets. The 4.5% baseline is NFL/NBA.
Skipping when only one sharp book is quoting. Then you have v4_single, not v4_full. Note it and size smaller.