Survey Results: PECOTA

I recently posted this survey question:

Sometimes, information from Baseball Prospectus’ PECOTA player projection system is used on MLBTR. Should we continue to post this information?

Over 2,000 MLBTR readers responded; about 90% said yes, continue using it.  The basic vibe of the comments was that more info can never hurt, even if we all acknowledge that a projection system isn’t gospel.

Many readers requested info explaining what PECOTA is and how it works.  Wikipedia does a very nice job giving the basics.  This is an oversimplification, but basically PECOTA projects a player’s future performance by looking at comparable players throughout baseball history.

How did PECOTA do trying to predict the 2007 season?  It led all projection systems with a .451 correlation coefficient for pitchers.  (A perfect set of predictions would have a coefficient of 1.0).  PECOTA also had the highest correlation coefficient in predicting hitters for ’07, at .627.  ZiPS, a free system from Baseball Think Factory, was close behind.  As you can see, pitcher performance is very difficult to project.