Looking at the late 80s/early 90s, it seems like players rarely switched teams in free agency. When did that start to become a more normal occurence?
Everything was a pain in the ass 30-40 years ago. It’s a lot easier to move nowadays
Unrestricted free agency began in earnest around the end of the 1980s. But in terms of rapid player movement, that didn’t really happen for about another decade. It probably started with Shaq in 1996 and then really picked up steam with Orlando’s attempt to build a superteam in 2000.
In 2012 players were able to keep their Bird rights when switching teams so that took away one reason not to leave. Also around then Owners got the contract structure changed to short cookie cutter contracts. This allowed players to be free agents more often. Also because contracts are standardized made negotiations easier.
Every CBA over the past few, the league has mandated shorter and shorter length contracts. In the 90s, I remember guys signing contracts that went for 7, 8, or 9 years (or even longer). Now, contracts go for 3, 4, or 5 years. With all contracts being shorter, the number of free agents each year has correspondingly gone up. More free agents mean more player movement on average.