Percent above league average.

I wish baseball-reference.com had versions of OPS+ for other batting stats, i.e., factoring year and parks: BA+, SLG+, ...

A few years ago for seasons, not career, I figured percent above league average for slugging average (SLG) and batting average (BA).

SLG:
In only three seasons was it above 100%, i.e., more than double the league average:

Ruth 1920 119.3%
Ruth 1921 107.3%
Bonds 2001 103%

This is followed by Ruth, Bonds, Ruth, Bonds, Gehrig, Williams, Williams, Ruth, Ruth, Foxx.  Ty Cobb 1909 DET  67.28% was number 100.

One batter slugged more than 50% below the league.  Here are the three worst:
Bill Bergen 1909 BRO -50.25%
Wayne Tolleson 1987 NYA -43.43%
Dal Maxvill 1970 SLN -43.09%

BA:
There were only 12 seaons in which batters were more than 50% above the league.  Only 2 of those 12 were after 1917, both by Ted Williams: 1957 52.25%, 1941 52.24%.  They are ranked 10 & 11.  Ty Cobb takes 7 of the top 12.

Best: Nap Lajoie 1910 CLE 58%.
Worst: Bill Bergen 1909 BRO -43.1%    Bergen was also worst in SLG.
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Why is the top slugger more than twice as much above the league as the top BA: 119 to 58?