Demographic formula reveals surprisingly short careers for MLB pitchers

Aug. 3 (UPI) -- Until now, statisticians had mostly given up on trying to keep track of the career lengths of pro athletes.

However, a group of demographers have developed a surprisingly simple way to calculate the working life expectancies, or "life tables," of baseball pitchers.

Researchers used a concept called a cohort change ratio to calculate the fleeting life tables -- 3.99 years on average -- of major league pitchers.

"The easiest way to explain a cohort change ratio is with an example," David Swanson, a sociologist and applied demographer at the University of California, Davis, told UPI.

"Worldwide, persons born in 2008 are the birth cohort of 2008," Swanson said. "If you divide the number of people worldwide aged 1 in 2009, the persons born in 2008 who have survived one year, by the number born in 2008, we have a cohort change ratio of those born to those who survived one year."

For every subsequent year, there is a cohort change ratio.

"If we divide the number of worldwide people aged 10 in 2018 by those born in 2008, we have a ten-year cohort change ratio."

Though there are some slight statistical nuances involved, Swanson said the methodology is more or less as simple as it sounds.

Swanson and his research partners didn't invent the methodology -- the cohort change ratio was first detailed in the journal Social Forces in 1962 -- but they are among the first to apply it to the task of measuring pitchers' life tables.

Why didn't someone think of using such a simple solution before?

Swanson, who specializes in applied demographics, said researchers in the field of academic demography often mistake complex solutions as superior solutions.

"Academic demographers -- and statisticians -- strive to achieve precision at any cost and length of time while applied demographers -- and statisticians -- are interested in achieving precision at the lowest cost and in the least amount of time," Swanson said.

Swanson and his colleagues all have an interest in baseball, ranging from "modest" to "above average" in their enthusiasm for the sport. But an affinity for America's pastime doesn't explain their choice of the sport as research subject. It was the long history of prodigious record-keeping that made baseball the logical choice for their work.

"We selected pitchers because they tend not to change positions -- unlike, say, an outfielder who later in his career plays first base," Swanson said.

Swanson and his research partners plan to submit their work to a peer-reviewed journal sometime in the near future.