How Many Games Will Be Played
In The World Series?

by Clement Washburn

Soon it will once again be time for the World Series of baseball. Tens of millions of dollars will ride on whether there will be a series of six or seven games with zillions of dollars made from selling advertising minutes or a four-game series with so little money made from advertising that the broadcasting network will lose, big-time.

Many of us recall the 1990 series when CBS lost over one hundred million dollars because they paid a hefty price for the rights to telecast the series and Cincinnati beat Oakland [*] in four straight games.

Is it possible to predict the number of games that a World Series will run? It may surprise some fans but the answer is, Yes. If we assume that generally the teams are equally matched, which as we shall see, is often the case, then we can predict the average result. It's much like calling heads or tails in flipping a coin. You know at the outset that half of the time the coin will come down heads and the other half of the time it will come down tails. Not so obvious is the fact that a quarter of the time it will fall showing heads (or tails) twice in a row and so on.

Here are the results of such a probability analysis of the expected results of a World Series: One-eighth of the time there will be a 4-game series; a quarter of the time there will be a 5-game series; 6- and 7-game series are equally likely and will occur five-eighths of the time. [Notice that a 4-game series is expected exactly as often as we would expect a coin to come up heads (or tails) in four tosses.]

Using the World Almanac, we can check the accuracy of these predictions against the actual historical record which runs from the first series in 1903 to the latest series studied, that of 1999. During the last century there were 93 series. (In two years, 1904 and 1994, there was no series; in 1919 and 1921 the series ran for eight games, the National League winning 5 to 3 both times. These four years are omitted from the following summary comparing expected number of games played with the historical record.)

Actual and Expected
Number of Games Played
in 93 Years of the World Series

4 games  5 games  6 games  7 games

Actual number: 18  20  21  34

Expected number:  11.6  23.3  29  29

The predictions are certainly not a hundred percent accurate but they're close enough to the actual results to provide guidance to the networks in their advertising plans. They can also help the planning of the teams' managers, the players and the fans.

It seems odd that there are historically 13 more 7-game series than 6-game series when the expectation is that there should be an equal number of each. Can this be because the team that is leading 3 to 2 after five games have been played will decide to save their best pitcher because they don't have to win the next game to stay in the series; the team that is behind, 2 to 3, must use their best pitcher since another loss will mean a loss of the series? This would help explain why a 6-game series will more often go on for another, final game.

* Thanks to the alert reader who (10-25-2003) corrected the original text, which read "Oakland beat San Francisco".
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Copyright © Clement Washburn 2003