Most people think Bryce Harper's decline is almost a sure thing - including me - after his Ted William-esque 2015 season, when he posted 197 wRC+. I went on to look how players in Harper's situation have performed and this is what I found:
18 players have put 41 seasons of 197+ wRC+ since 1871, an average of ~211 wRC+. I calculated the average drop-off on the following year after recording that season, just to be surprised that it is only 26 points lower. That means, on average, those players put up 184.5 wRC+ seasons after having 197 or better wRC+ seasons. That number is somewhat skewed by Babe Ruth and Barry Bonds who averaged 201 under that situation. We all know Bryce Harper is probably no Ruth or Bonds, so I removed them from the data, and went ahead and calculated the historical drop-off. Well, the rest had a nice average of 172 wRC+ on the season after a 197+ wRC+ season. So, it does not seem to be a huge performance cliff after having a monster season - if you are good enough to reach that number, it's probably because you are legitimately good and will continue to be so.
I know this is nothing more than a fun fact but still puts his 164 wRC+ Steamer projection in perspective quite nicely. Makes you wonder if Steamer projection is rather conservative, especially considering Harper's age (23 years old). On the other hand, the six players with seasons under 164 wRC+ were considerably older than Harper at that time e.g. on average ~31 years old. Here are the numbers:
*Ted Williams did not play from 1943-1945, therefore N+1 is considered to be 1946.
By Oswaldo Gonzalez