Mains: Why PECOTA hates your favorite team in 2019

From SABR member Rob Mains at Baseball Prospectus on February 7, 2019:

Baseball Prospectus first published PECOTA projections for players and teams in 2003. In the ensuing 16 seasons, through last year, we projected that the Pirates would win 1,202 games. The Pirates, since 2003, have, in fact, won 1,201 games. Good job, PECOTA!

That overall number, though, smooths off a lot of rough edges. In 2006, PECOTA thought the Pirates would win 79 games. They won 67. It overshot again in 2010, expecting 72 wins, getting just 57. But it missed the boat the other way, expecting just 79 wins in 2013, when the team won 94. And PECOTA saw Pittsburgh as an 80-win team in 2015, when it went on to win 98.

So take the following graph with a grain of salt. It shows the cumulative error that PECOTA has made over its 16 seasons for all 30 franchises. A positive number indicates that PECOTA was overly optimistic, a negative number means it was overly pessimistic. Keep in mind that these totals smush together positive and negative outlier years.

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Originally published: February 7, 2019. Last Updated: February 7, 2019.