The Best and Worst of the American League

This is my first follow-up to "Has Baseball Become More Competitive?" Here I draw on the first two graphs from that post to make some observations about the best and worst teams in the history of the American League. My metric is the centered, nine-year won-lost (W-L) record (see "...Competitive?" for more about the metric). For reasons given here and here, I eschew performance in post-season play as a measure of excellence.

The graphs (to enlarge, right click and select "open in new tab"):

Remember, I am measuring performance over nine-year spans -- not individual seasons -- so the following lists will not always correspond with lists of teams having the best and worst W-L record, by season. Using the nine-year, I present the best (E = expansion team)...

Athletics (then of Philadelphia), 1905-11
Red Sox, 1912-1917
White Sox, 1918
Yankees, 1919-62
White Sox, 1963
Yankees, 1964
Orioles, 1965-81
Yankees, 1982-85
Blue Jays (E), 1986-90
Athletics (then of Oakland), 1991-92
White Sox, 1993
Yankees, 1994-2003

...and the worst (E = expansion team)...

Twins (then the original Washington Senators), 1905-08
Orioles (then the St. Louis Browns), 1909-15
Athletics (then in Philadelphia), 1916-22
Red Sox, 1923-32
Orioles (still the Browns), 1933-37
Athletics (still in Philadelphia), 1938-47
Orioles (still the Browns), 1948-54 (tied with Athletics in '54)
Athletics, 1954-64 (tied with Browns in '54) (A's in Philadelphia through 1954; in Kansas City, 1955-67)
Rangers (E), 1965-72 (as the expansion Washington Senators, 1965-71; as the Texas Rangers, 1972)
Brewers (E), 1973-74
Indians, 1975
Angels (E), 1976
White Sox, 1977
Twins, 1978-79
Athletics (in Oakland), 1980
Mariners (E), 1981-85
Indians, 1986-89
Mariners (E), 1990-91
Tigers, 1992-2001
Devil Rays (E), 2002-03

I take these lists (especially the list of worst teams) as further evidence that baseball has become more competitive since the onset of expansion and free agency. Just look at the number of original franchises at the bottom of the heap since 1965.

There's more to come, in future posts.