Expected Value (EV) is the long-run average profit or loss of a bet if you could place it thousands of times. A positive-EV (+EV) bet is one where the odds on offer are bigger than the true chance of winning deserves. Bet enough +EV spots and the maths grinds out a profit — the same way the house edge works, but in your favour.
Why bookmakers can be beaten
To guarantee profit, bookmakers add a margin (the "vig") on top of the true odds, and different books disagree on prices. Sometimes one book is simply too generous. That gap — between the price offered and the true line — is your edge.
A simple example
Say a match is a true coin-flip — each team has a real 50% chance. Fair odds for 50% are 2.00. A book offering 1.90 is charging margin (−EV). A book offering 2.20 is paying more than fair (+EV).
EV% = (0.50 × 2.20) − 1 = +10% — on average, 10¢ profit per $1 staked.
How Starline finds it
We de-vig the sharpest prices to derive each outcome's true probability, compare every bookmaker against that fair line, flag the ones paying over the odds, and suggest a Kelly stake. Any single bet can still lose — the edge shows up over volume.