Many people believe that the world's best professional sports bettors, like Billy Walters, win at least 60 percent of their bets. It's understandable that people think that, but it's just not true. The fact is, the difference between the percentage of bets won by successful sports bettors and the percentage of bets won by chronic losers is relatively small.
Professional sports bettors rarely sustain a long-term winning percentage higher than 55 percent, and it's often as low as 53 or 54 percent. People find this hard to believe, and they understandably get even more skeptical when told that, for a genuine professional-level sports bettor, a long-term winning expectation of 60 percent or more is actually too high.
We'll ignore money line bets here for the sake of clarity and address only those bets wherein the player must risk as much as 11 to win 10; pointspreads and over/under bets. Against this type of bet, anyone at all can expect to win 50 percent. After all, the only thing required is to flip a coin and pick a side. The bookmakers' profit comes from the difference between what a bettor must risk and what a bettor expects to win. Every time a player wins, the bookmaker withholds slightly more than 9 percent of the winnings ($1 for every $11 risked). Consequently, a bettor winning only half his bets will ultimately go broke.
In this vein, a winning percentage could actually be too high. This sounds crazy at first, right? But there's a simple explanation: If a bettor has five bets on a given day, risking $110 to win $100 on each bet, and wins three of them, that's a great winning ratio of 60 percent and a net profit for the day of 80 dollars. (The bettor wins $300 and loses 220 dollars.) If another bettor has fourteen bets on that same day, risking $110 to win $100 on each one, and wins eight of them, that's a much poorer winning percentage of only 57 percent, but almost twice as much profit for the day of 140 dollars. (The bettor wins $800 and loses $660.)
The second bettor was not necessarily less skilled at picking winners than the first bettor; rather, the second bettor may simply have chosen to apply all his advantages - including those which had less than a 60 percent chance of winning in the first place. If the ultimate goal is to make money, it is obvious which of those two bettors was more successful. The real goal is, of course, to make money. The measure of success of a sports handicapper is not his percentage of winning bets, but the relative amount of profit he makes over any given period of time.
Although there are, indeed, propositions that offer more than a 60 percent expectation of winning, such propositions are relatively few and far between, and are only a very small part of the overall picture. With the break-even point at about 53 percent, genuine professional bettors know there is no tenable excuse to pass up propositions offering expectations of higher than, say, 55 percent. A small advantage applied over and over is awesomely effective.
Mathematicians will confirm that a profit is more assured from a group of 200 bets with a 55 percent expectation-per-bet than from a group of 50 bets with a 60 percent expectation-per-bet. In other words, the more bets placed, the more predictable the outcome.
That, too, is one of the facts of life of which successful bettors must be familiar. It's a basic principle of math: The more bets you are able to place, the more likely it is that your winning percentage will be close to your expectations. A pro bettor must be more concerned with profit than with establishing a great winning percentage, and those two conditions are not always compatible. A real pro applies all his advantages as often as possible, not only the best of his advantages when they occasionally arise.
To illustrate the point, consider casino craps. The house has less than a 51 percent winning expectation against a passline bet at craps, yet casinos advertise their craps games on signs 100 feet tall. Casino executives know that if they can get enough players to make enough bets they will end the day with approximately the percentage of profit expected. They also know that the fewer bets placed, the less predictable the percentage of winning bets. Can you imagine a casino wanting to limit the number of times you throw the dice?
The accompanying illustration (above) shows the results of different winning percentages over different numbers of bets when risking 11 to win ten. Standard vigorish charges of 4.55 percent are figured into the numbers. (The bookies' net commission is 4.55 percent of all monies risked when bettors risk 11 to win ten.) Notice in the illustration that winning 55 percent of 250 bets is more profitable than winning 65 percent of only 50 bets, and remember that a profit is more assured, that is, more dependable, because of the higher number of trials.
Mathletics: How Gamblers,
Managers, and Sports
Mathematics in Baseball,
Basketball, and Football
by Wayne Winston
Princeton University Press
How Do Bettors
Make Money Gambling?
Let p = probability that a gambler wins a point spread bet. If 10p-11(1-p) = 0, our expected profit on a bet equals 0. We find that p = 11/21 = .524 makes our expected profit per bet equal to 0. Therefore, if we can beat the spread or totals more than 52.4% of the time we can make money. Suppose we are really good at picking games and can win 57% of our bets. What would be our expected profit per dollar invested? Our expected return per dollar invested is (.57(10)+.43(-11))/11 = 8.8%. Thus if we can pick winners 57% of the time we can make a pretty good living betting.