Same-Game Parlay, in plain words
A same-game parlay, or SGP, combines several bets from the same game into one ticket. Unlike a normal parlay, the legs are often related: a quarterback's passing yards and the top receiver's receiving yards tend to rise and fall together.
When legs move together, the chance they all win is higher than multiplying their separate chances suggests. Books know this and price same-game parlays with their own correlation adjustments, usually leaving a wider margin than on separate bets. So the payout is rarely the simple product of the legs.
The edge, when there is one, comes from correlations the book prices badly: legs that move together more, or less, than its model assumes. Finding them means measuring how often the legs actually landed together, not how often they each landed alone.
The idea, drawn
Worked example · illustration
Two legs, each a 50% chance
- Each leg
- 50%
- If independent
- 25% (+300)
- If they move together
- 30% (+233)
- Illustration
- Assumed joint rate
- Independent legs: 50% x 50% = 25%, a fair +300.
- Suppose the legs land together 30% of the time instead. The fair price drops to +233.
- A book that priced the pair as independent would be offering too much; one that prices the correlation and adds margin offers less.
Correlation changes the fair price. The number to compare is the joint chance, not the product.