NBA Shooting Efficiency: Historical Peaks and Valleys

Attempting to evaluate shooting performances across NBA history will lead to some peculiar results.  How could Neil Johnston shoot just 45% from the field but lead the league in 1957?  Skip ahead to 1980 and find Adrian Dantley shooting 58% from the floor, good for only fourth highest in the NBA.

Era Is Relevant

One way to evaluate players across era's is to compare their output to a common benchmark like league average Points/True Shot Attempt in each season.  Utilizing a metric like True Shooting+ takes wacky looking statistics and places them in the context of their time.    

It turns out that in 1957 Neil Johnston scored 121 points for every 100 shots when his season is normalized over all of NBA history.  Dantley's True Shooting+ in 1980 was a tick lower at 119.