Vig range filter: bookmaker margin in backtests

What the vig range filter does

The vig, or bookmaker margin, is the overround built into the odds: the amount by which implied probabilities sum past 100 percent. This filter computes a team's average closing vig on a market's main line, moneyline, spread or total, across its last N matches, expressed as a fraction where 0.02 means 2 percent, and keeps the matchup when that average falls inside your band.

Why the margin is a market-quality signal

Bookmakers do not price every market with the same confidence. Where liquidity is deep and information plentiful, margins compress: a 2 percent vig signals a market sharp enough that beating it consistently is hard. Where matches are obscure and models thin, margins widen to protect the book, and wide margins often coexist with lazier, slower prices. Filtering on vig therefore selects the market environment your strategy operates in: hunt soft markets where mispricings survive longer, or restrict yourself to sharp ones when you want your backtest's edge to have cleared the hardest test available.

Example strategies

• Keep matchups where the average moneyline vig runs above 4 percent, focusing a form-based angle on softer, less efficiently priced fixtures.
• Require vig below 2.5 percent as a robustness check: an edge that survives on the sharpest prices is far more likely to be real.

Combining it with other filters

Vig is one lens on market quality; league liquidity is the other, gating on Pinnacle betting limits instead of margins, and the two together map the sharp-to-soft spectrum precisely. Add league line move to find leagues whose prices also drift a lot after opening, then layer your actual angle, form, schedule or price, inside that environment. This is a Pro filter.

Market-quality effects are subtle, which is what makes backtesting them against real Pinnacle historical odds so valuable. Set your vig band and backtest it in the Strategy Builder now.