Is there value in parlay cards

Oct 9, 2006 4:05 AM

Readers, please forgive me if I take a one week excursion from keno, but I had the opportunity yesterday to read a few columns written by the astute Mr. Huey Mahl for this paper a few years ago. They inspired me to take a brief look at football parlay cards.

Mr. Mahl gave a cogent explanation of how the vig (vigorish, or house percentage in bookie parlance) is figured. This brings up the question, given a certain vig, what percentage of winners must we pick against the spread to break even on a parlay card? One difference between a parlay card, a 10-teamer say, and a 10 spot keno ticket is that each pick on the parlay card is an independent event. The ten spots on a keno ticket are not independent. (The selection of one ball on the keno ticket reduces the chance of the next ball being called.)

The point spread on the parlay card is established to come as close to a 50/50 proposition on each game as is possible, and the outcome of each game does not influence another. These properties give rise to the true odds and the vig as Mr. Mahl explained.

Given these facts, we can set up the following simple equation to determine the percentage of correct picks that are required to make any parlay card a break even proposition:

T x (log X) = log (1/P)

In the equation, X = the required percentage of correct picks, T = the number of teams picked, and P = the parlay card pay off odds for one.

Solving this equation for X for a hypothetical parlay card with a straight 25% vig as below gives these results:

                

Teams True Odds Parlay Pays Vig  X Pct.
3 8 6 25.00% 0.55032120814 55.03%
4 16 12 25.00% 0.53728496591 53.73%
5 32 24 25.00% 0.52961192052 52.96%
6 64 48 25.00% 0.52455753171 52.46%
7 128 96 25.00% 0.52097681371 52.10%
8 256 192 25.00% 0.51830732481 51.83%
9 512 384 25.00% 0.51624051598 51.62%
10 10224 768 25.00% 0.51459300448 51.46%

As you can see, you must be able to pick slightly better than 55% winners against the spread to break even on this card if you play three teamers. The required percentage of correct picks steadily declines until, playing ten teamers, it is only required to pick about 51 1/2 percent winners against the spread to break even!

We can deduce several things from these somewhat surprising figures.

1. The bookie’s point spreads must be very good indeed, because if they weren’t very close to a random distribution parlay card players could beat them badly.

2. There obviously aren’t as many good football handicappers as we think there are. I think that most people who play parlay cards think that they can beat the spread 55% or even 60% of the time, but if this were true, there wouldn’t be any parlay cards.

3. If you have any talent at all for beating the spread with your picks, you are much better off playing ten teamers than three teamers!

Well, that’s it for now. Good luck! I’ll see you in line! email: [email protected]