This paper explores the changing competitive balance in Major League B
aseball through the relative-entropy measure of information theory. It
is shown that while competitive balance in both leagues has been on a
n upward path during the 20th century, the path has had numerous detou
rs that resulted from some on-the-field and some off-the-field changes
that Major League Baseball has undergone during the past 75 years. Th
e most important detours occurred in the wake of the Black Sox scandal
of 1919, Jackie Robinson's breaking the color barrier and the concurr
ent spread of television and erosion of the minor leagues, franchise m
oves and major league expansion, and free agency.