Standard wisdom on parlays: they're a tax. The math is brutal — combine multiple bets and the sportsbook gets to charge vig on each one, eating any edge before you place the slip. Standard wisdom is right about uncorrelated parlays. It's wrong about correlated ones, when you know what to look for.
Why most parlays lose money
When you parlay two independent bets, the payout is the product of their individual odds minus the compounded vig. Two -110 bets parlayed = +260, but the fair-juice price is +300. You're handing the sportsbook a 10% overround on top of the vig you already paid on each leg.
