Why pros parlay for profit
A common myth surrounding professional gamblers is that we don't parlay, but a more accurate assessment would be that we don't parlay often. An equally true statement is that we love parlays. We love them because the odds are incredibly in our favor.
Sportsbooks also love parlays because they make way more vig on parlays than on straight wagers. Sound strange? How can a proposition be both hugely favorable to books and professional gamblers at the same time? Let me explain.
While most sportsbooks struggle to achieve the Theoretical Hold Percentage of 4.55 percent on straight wagers, three-team parlays routinely achieve Practical Hold Percentages over 12 percent.
Basically, you're paying at 6-1 on a proposition with true odds of 7-1. Assuming oddsmakers have made a reasonably effective pointspread, or assuming bettors typically pick correctly 50 percent of the time (both of which are true statements), it is easy to see why sportsbook managers encourage parlays. Nothing gets your hold percentage up like a healthy diet of parlay action.
Here's the math:
((7+1) - (6+1)) / (7+1) = (8-7) / 8 = 12.5%
If the bookie math is throwing you, consider from a player's perspective that a three-team parlay has eight possible outcomes, seven which favor the house and one which favors the player. Hence the true odds of 7-1. However, the standard pay out for a three-team parlay is 6-1.
That overlay (the difference between the payoff and the true odds) is the house vig. One full point overlay on eight possible outcomes, or 1/8 equals 12.5 percent. That's the house commission on three-team parlays. As you add teams to your parlay, the theoretical hold for the house skyrockets as follows.