If you want to root out the effect of flukes in the short series (but I think it ends up evening out over a 30-year sample anyway), you could look at how many different teams have had a certain number of 90-win+ seasons in those 30 years versus teams in the other sports with comparable win percentages. Something like that.

A lot of baseball’s parity is true at any level of the game, from little league to college to the majors; it’s not necessarily that MLB as an organization does any better than the NBA or NFL or other leagues at designing its playoffs or schedules or roster/free agent/draft rules, etc. (though I do think there’s more parity in the majors than in college because the best college recruits go to the schools with the best traditions/programs and sometimes the most resources, which is not true in the majors).

The very play of the game involves so many variables and strategies. So much relies on the pitcher and how many runs he gives up, and it’s frickin’ hard to pitch and hit well night in and night out, even if you’re a vaunted team like the Yankees. If you’re a star on a team whose pitcher has just blown it, your chance to make up the difference only comes when you’re at the plate, and you can then only produce as many runs as there are runners on base plus yourself. If you’re a star on a basketball team, you can go steal the ball and score two or three points in a matter of seconds, plus one if you get fouled in the process. Baseball is a complex, confounding, and frustrating game; on any given day, any team can win, which is not true in really any other sport as much as it is in baseball. Over time, if you have good management, motivated players, and solid pitching, you can get into the playoffs and win a championship even if, on paper, you don’t have the most talented players. Stars have less of an opportunity to impact a team, a game, and a whole season in baseball because there are so many other players who have to do their job on a regular basis.