There has been a small flurry of retirement announcements recently, with Kris Benson and Trevor Hoffman announcing their retirements this week. Billy Wagner already announced that 2010 was his last year, and Andy Pettitte just admitted that he wouldn’t be suited up for the beginning of the year, at least, though he wasn’t certain about the rest of the season. With their retirements in mind, as well as the work of Tom Tango and others on the current and increasing Hall of Fame logjam, I started to wonder how many good players tend to retire in any given year.

Of course, many retirements aren’t strictly announced — some players get injured and just never come back, some players sign a minor league deal and never get called up again, some players just fade away, and some players are Rickey Henderson. So for my purposes, I’ll consider “retirement” to be a player’s last appearance in the major leagues, and I’ll consider a “good” player to be someone who’s made at least one All-Star appearance. Somewhere around half of them will make it to the Hall of Fame ballot — this year, 16 of the 30 “good” players who retired in 2005 made it to the ballot, along with three others who never played in an All-Star game, Kirk Rueter, Bobby Higginson, and Lenny Harris.

There are 616 players in my sample, former All-Stars who played their last game between 1977 and 2006. It turns out that the number of good players who retire in any given year is remarkably consistent, despite two league expansions and recent All-Star roster expansions. In any given year, about 20.5 good players retire. (The average is 20.5 and the median is 20.5; round up if you want, but you’ll lose half a player either way.) Their average age at their final game is also remarkably consistent, right around 36 every year.

How consistent has it been? The average number of players who retired from 1977-1991 (20.4) is almost exactly the same as the average number of players who retired from 1992-2006 (20.7). And the median number of players in each subset (21 and 20) is almost exactly equal to the average. In other words, the rate has stayed constant over time, virtually unaffected by expansion. Nor was it affected by strikes — 1981 had the lowest number of retirements, nine, but 1994 was exactly average with 20. The maximum of 30 has been reached three times, in 1987, 1989, and 2005.

So what does this mean? Well, this is another way of understanding the Hall of Fame logjam — every year, 20 prominent players stop playing, and five years later, many or most of them merit consideration for the Hall of Fame ballot. It has become especially clear in the last decade. Cal Ripken and Tony Gwynn both hung up their spikes after the 2001 season, and easily marched into the Hall five years. later. Exactly two other players who played ball after Gwynn and Ripken have made it into the Hall, Roberto Alomar and the aforementioned Rickey Henderson. Yet hundreds of other “good” players have retired in the meantime, and many of them will likely face the same unlucky fate that met John Franco, Kevin Brown, and 12 others who fell off the ballot on their first try.

Ballplayers retire at the same age and in the same numbers as they have done for the last three decades. Hopefully, an enlightened Veterans Committee will begin to clear the logjam. After all, in 2011, another 20 good players will likely play their last.