Sabermetrics for Dummies: Part 2 – P.E.C.O.T.A.


(Nate Silver, who developed PECOTA, is one of Time’s 100 Most Influential People in the World)

As stat-tracking technology becomes better and better, and budgets become tighter and tighter, baseball teams are starting to turn to numbers, or sabermetrics, to determine the worth of their players. These are a few of the statistics that all teams use to evaluate players.

Today’s stat: P.E.C.O.T.A.

It’s only part two of this series and the acronyms are already at six letters. If that doesn’t scare you off, learning the meaning of PECOTA will. It stands for “Player Empirical Comparison and Optimization Test Algorithm.” It was developed by statistician Nate Silver in 2002. If you don’t know who Nate Silver is, just know that he predicted the exact results, state for state, of the Obama vs. Romney 2012 presidential election weeks before Election Day. So he’s pretty good at this prognostication business.

PECOTA is a system for forecasting the performance and career development of baseball players. It does this by comparing current baseball players to a database of nearly every single major and minor leaguer that has had stats recorded since World War II.

When analyzing current players, PECOTA will match them with comparable major leaguers based on something called “similarity scores.” These scores are determined by four different factors: production metrics (batting average, walk rate, strikeout rate, etc.), usage metrics (plate appearances, innings pitched, etc.), phenotypic attributes (height, weight, age), and position (infielder, pitcher, etc.).

Players are then matched up with those they appear similar to. By looking at how the comparable players finished their career, it is easier to predict how the player in question will finish his.

PECOTA is unique to other projection sabermetrics because it analyzes players based on a three-year window that they are in compared to similar players in a similar three-year window.

Baseball Prospectus (the website that operates PECOTA) uses this projection system to predict what will happen days, months, and years into the future. In February they came out with their 2013 season predictions based on the PECOTA principles. In this prediction, the Sox finish second in the east and keep on playing after game 162. Nate Silver’s statistics we’re dead on about Massachusetts being an “Obama-Biden” state, let’s hope they’re right about it being a playoff baseball state as well.

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