just a quick one, since ESPN published a new kind of adjusted Plus-Minus yesterday (called real Plus Minus, RPM). I don't want to go too far into the merits of either stat. I am pretty sure that RPM has problems like every adjusted PM before and PER is basically just 'boiling down more common stats to one number', but it were the two things I just had at hand. If somebody gives me a table that has both RPM and another adjusted plus minus, I'll gladly repeat the following, which is doing a simple linear regression. I know the word sounds dangerous, but linear regression is basically complicated for ' draw a line through your data and check how far stuff is away from this line'. Using 293 players that played at least 48 games, the correlation between RPM and PER is 0.52, which can be described as 'existing, but not very high'.
As you can see, the top of the game are still LeBron and Kevin, but there are some clear outliers.
Now, drawing the line through the data and then showing if the PER is above or below this line, we get the following picture:
Have a nice evening,