James’ “Pythagorean Theorem”

 

 

         In the mid-1990’s, a man named Bill James developed a formula that predicted the percentage of games a team is to win based on the number of runs scored and runs allowed.

 

 

Win % = (runs scored)^2 / [(runs scored)^2 + (runs allowed)^2]

 

 

You can see that he used the Pythagorean Theorem in a round-about way:

 

(runs scored)^2 = (runs scored)^2 +(runs allowed)^2, where runs allowed =0.

 

Note:  This formula is not exact.  Bill James used this formula as a tool not as an exact science. 

 

-  For example, the 1998 Yankees scored 965 runs and allowed 650 for an estimated winning percentage of (965^2)/(965^2 + 650^2) = 931,225 / 1,353,725= .688.  So, for a 162-game season, this means the Yankees had approximately 111.5 wins. However, they actually won 114, so the formula was off by a little more than two wins.

 

 

There were some variations of James’ “Pythagorean Theorem:

 

A basketball analyst, Dean Oliver, applied James' Pythagorean theory to his own sport, the result was similar, except for the exponents:

 

 

Win % = (Points For)^14 / [(Points For)^14 + (Points Against)^14]

 

 

Steven J. Miller models game runs of professional sports leagues in general:

 

 

Win % = (runs scored)^a / [(runs scored)^a + (runs allowed)^a]

 

Where a=1.82 for baseball, 13.93 for basketball, etc.