Loyalty to petrified opinions never yet broke a chain or freed a human soul in this world-and never will.
—Mark Twain

Mine honesty and I begin to square.
The loyalty well held to fools does make
Our faith mere folly; yet he that can endure
To follow with allegiance a fall'n lord
Does conquer him that did his master conquer
—William "Author" Shakespeare, Antony and Cleopatra.

Why do you hurt me, Michael? I've always been loyal to you.
—Tom Hagen, The Godfather: Part II

The other day on the SABR-L email digest, there was a note from John Thorn from a reader to the effect:

I came across a transcript of an interview you did with "Outside the Lines" a few years back. You mentioned during the interview that player tenure on teams lengthened during the 1940s and 1950s, and I was wondering if you had any statistics to that effect.

I won't go into the idea of loyalty in player movements, whether it's a matter of disloyalty, if you want to call it that, on the part of the owners or the players or whether this is just a business like any other where employees move around from time to time. (If you want a treatise on management disloyalty, you revisit Ford's recent history, but I digress.) However, I can and did investigate how long it took a player, for whatever reason, to switch teams.

First, here is a breakdown by a player's first team per decade. For each decade, here are the average years he spent with that team (whether he went to another or left the majors) and the average number of years he spent in the majors. Finally, the percentage of his major-league time spent with that first team appears in the last column:

Note that the data for the current decade (and possibly for the 1990s) are incomplete. The number of years with the first team were way down but the percentage of total time is way up. Clearly, more time is needed to examine the 2000s.

The numbers for the 1990s are also down from the previous forty years. It may be due to incomplete data for current players.

Next, let's look at the average life expectancy for a given player when he starts his tenure with a new club (either as a rookie or as a veteran on a new ballclub) over the years. Below are the average stats for all of those new tenures per decade:

Again, we do not yet have complete data for the last decade or so. However, you might note that the average tenure had held pretty steady in the 2.5 to 2.75 years range from the Twenties to the Eighties. Actually, it went up slightly in the expansion era, and even free agency didn't put much of a dent in it.

But, you'll also note that the average career length went up, meaning that the percentage of time that a player spent with any one individual team went down on average.

If you want to argue that expansion helped marginal major-leaguers stay in the game longer, the data seem to support that. However, if you want to look into any concept of player/owner loyalty. All parties seem to remain as loyal as ever to each other, whatever that means.