Playoffs
Yankees 15 in 16 0 losing seasons
Braves 12 in 16 2 losing seasons
Red Sox 9 in 16 1 losing season
Cardinals 8 in 16 4 losing seasons
Indians 7 in 16 6 losing seasons
Dodgers 6 in 16 3 losing seasons
Astros 6 in 16 4 losing seasons
Angels 6 in 16 5 losing seasons
Twins 6 in 16 7 losing seasons
Giants 5 in 16 6 losing seasons
Athletics 5 in 16 7 losing seasons
DBacks 4 in 13 6 losing seasons
Phillies 4 in 16 7 losing seasons
Mariners 4 in 16 7 losing seasons
Cubs 4 in 16 8 losing Seasons
Rangers 4 in 16 9 losing seasons
Padres 4 in 16 9 losing seasons
White Sox 3 in 16 6 losing seasons
Mets 3 in 16 7 losing seasons
Rockies 3 in 16 10 losing seasons
Miami 2 in 16 10 losing Seasons
Rays 2 in 13 10 losing seasons
Reds 2 in 16 11 losing seasons
Orioles 2 in 16 14 losing seasons
Tigers 1 in 16 12 losing seasons
Brewers 1 in 16 13 losing seasons
Blue Jays 0 in 16 8 losing seasons
Nationals 0 in 16 12 losing seasons
Royals 0 in 16 15 losing seasons
Pirates 0 in 16 16 losing seasons
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Indy 13 in 16 3 losing seasons
New England 11 in 16 2 losing seasons
Green Bay 11 in 16 2 losing seasons
Philadelphia 11 in 16 4 losing seasons
Pittsburgh 10 in 16 2 losing seasons
Minnesota 8 in 16 4 losing seasons
Dallas 8 in 16 6 losing seasons
Denver 7 in 16 3 losing seasons
Miami 7 in 16 5 losing seasons
NYJ 7 in 16 5 losing seasons
Baltimore 7 in 15 6 losing seasons
NYG 7 in 16 6 losing seasons
Seattle 7 in 16 6 losing seasons
Tampa Bay 7 in 16 6 losing seasons
Tennessee 6 in 16 5 losing seasons
Jacksonville 6 in 16 7 losing seasons
Atlanta 6 in 16 8 losing seasons
SF 6 in 16 9 losing seasons
San Diego 5 in 16 5 losing seasons
Kansas City 5 in 16 7 losing seasons
St Louis 5 in 16 10 losing seasons
New Orleans 4 in 16 8 losing seasons
Buffalo 4 in 16 9 losing seasons
Carolina 4 in 16 9 losing seasons
Chicago 4 in 16 10 losing seasons
Washington 3 in 16 8 losing seasons
Oakland 3 in 16 9 losing seasons
Arizona 3 in 16 11 losing seasons
Detroit 3 in 16 12 losing seasons
Cleveland 2 in 13 10 losing seasons
Cincy 2 in 16 10 losing seasons
Houston 0 in 9 6 losing seasons
I'm basing this since the 1994 MLB strike. There's at least the perception that things changed in MLB after that.
Since the NFL has more teams in the playoffs the playoff numbers should be compared to "expected" appearances. If there was "true parity" each NFL team had an expectation of about 6 playoff appearances and MLB teams had an expectation of 4 appearances.
If you're looking at playoff appearances only. the quick conclusion is that it shows slightly less parity for MLB than the NFL. Only 1 NFL team made the playoffs twice as often as "expected" while 4 MLB teams did. Still 2 of the top 5 in playoff appearances are the small market Cards and Indians.
The losing season data is more convincing to me. There's too many teams that had losing seasons 75% of the time. Most, but not all, are small market teams that typically are near the bottom in payroll. OTOH some of the big money teams haven't had much success.( Cubs 1908 World Champions
) It's an advantage to have a higher payroll but it isn't anywhere near as decisive as commonly believed.