October 29, 2015

BP Unfiltered

On PECOTA, the Royals, and 72 Wins

by Sam Miller

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None of us ever thought that PECOTA's 72-win projection for the Royals would go quietly—it's just too rich to ignore when writing about Kansas City's two-game lead in the World Series. About a month ago, I performed a review on that projection for Fox Sports' JABO. It went like this:

There was something about the number 72 that seemed perfectly appropriate, an echo from Baseball Prospectus history. Our forecasting system PECOTA's most famous projection, if a projection can ever be really famous, came in 2007, when Nate Silver'€™s machine spit out a 72 for the Chicago White Sox. They were coming off a 90-win season, which had itself followed a World Series title. Oh, did people fume --€“ a Chicago Tribune response was so angry it earned a Fire Joe Morgan fisking, while Kenny Williams snarked that the projection was "€œa good sign for us because usually they're wrong about everything regarding our dealings."€ And then the White Sox won ... 72 games.

So on the night before we released our PECOTA projections at Baseball Prospectus this winter, and I saw with terror that we had put a 72 on the Royals. PECOTA keeper Rob McQuown and I went over every detail of that projection to make sure it wasn'€™t a mistake, and I was also amused. Maybe we'€™d hit another 72?

Nah. The Royals passed 72 in mid-August and are on pace to win 95. Once again, a 72 has become one of our most famous projections -- €”drawing, once again, snark from team execs, this time justified. What happened? Let's perform an autopsy.

There are three foundations to a projection system:

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Sam Miller is an author of Baseball Prospectus. Follow @SamMillerBB
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