Career Length Musings

While I was at the recent SABR convention I attended the Bio Project committee meeting where the aim is to record a biography for each of the more than 16,000 players who have played major league baseball. That got me to think about a) the difficulty of such a project as more players enter the league each year than biographies being written, and b) how many of these players are ones most of us have never heard of. And that got me to thinking about career length so I took a few minutes tonight to create the following two graphs.

The first is a pie chart that shows the percentage of players whose careers have spanned a certain number of years. Note that this includes 16,418 of the 16,556 players in the Lahman database (only those who show up in the batting or fielding record). And what it shows is that fully 53% of the players have careers that span four years or less and 74% span eight years or less (and I say span because it includes first and last appearance and not individual seasons).



The second graph shows the average career length by debut year. In other words beginning around 1900 career lengths were between four and five years which steadily rose until World War II when it dipped considerably as players who debuted in 1944 and 1945 had career lengths that averaged 3.5 and 3.3 years. The march continued on until it peaked around 1986 at 8.2 years and then began declining because an increasing number of players who debuted after that are still active. I could have excluded them but then of course that would have skewed the numbers for 1986 and after downward to include only players who are no longer active. The more recent are also skewed downward since it is common for minor leaguers to not appear in one or or more seasons after their debut.

Interestingly, there is also a dip in the 1977-1980 period which may be associated with the advent of free agency (coupled with expansion) as teams tried to stock up on younger players(?). I assume that the increasing career length can attributed to a number of causes which include (in descending order by importance); better medical care for players that enables them to play longer; higher salaries and therefore greater investment by teams and greater incentive by players to continue playing; the greater skill required to play the game at this level which engenders greater incentive to continue to improve and retain one's position.

It's also interesting to note that career length dipped slightly in the expansion years of 1961, 1969, 1977, and 1993.