With older major league players failing to secure long-term free agent contracts over the last few years, I wondered if year-to-year retention of players went down in recent seasons. For season, a query generated how many of those players appeared in at least one game, and how many of those returned for at least one game the next season. From these two numbers, query catcalled the percentage of players returning. Both the output of the query and a graph representing the year to year percentages can be seen in this spreadsheet.

Sometimes you start to look at one thing and find another that is just as interesting. The percentage of players retained jumps in 1960, 1961, 1968, 1976, 1992, and 1997. Each of these seasons preceded an expansion year. Teams did not want to expose prospects to the draft by giving them major league experience, so a few stayed in the minors a bit longer than they otherwise might, and veteran players hung around rather than being moved out for a youngster.

The study cover 1920 to 2019, the range of years in the Day by Day Database with a following season. In the 1920s, retention rates sit in the mid to upper 60s, then rise into the 70s in the 1930s. It could be that the depression drove a number of minor league teams out of business or more firmly into the grasp of major league organizations. This would have given players fewer options of finding work in an independent minor league, forcing them to stay in the majors.

The percentage hit a high point in 1940 at 75.3% of players retained, then World War II sent that plunging. In 1942, only 58.8% of players were retained.

The retention percentage quickly bounced back, rising to 73.6% by 1948. This held steady until the expansion 1960s. The chart shows a six-year moving average at 80% first in 1969, and it stays above 80% for twenty years.

Why the rise in retention? I believe that four expansions in seventeen increased the number of job available, without necessarily increasing the talent available to fill those jobs. Given the poor quality of expansion teams, it wasn’t like there was a ton of major league talent sitting at AAA just waiting for a chance. So teams kept marginal talent around longer because they needed it.

After 1984 the retention rate starts dropping again. The Caribbean starts contributing more and more players to the majors, helping to make up for the lack of talent. Note that the moving average of the retention rate even drops in the 1990s, despite two expansions providing a boost.

Around 2008, the retention rate flat lines at about 77%. There is no clear evidence that shorter term free agent contracts in the last few years really changed the retention rate. Once thing that is pretty clear, however, is expansion pushes rates higher. If the MLBPA wants their veteran members to play longer, they should push for another expansion.