Catcher's ERA or CERA in baseball statistics

Baseball statistics

Statistics play an important role in summarizing baseball performance and evaluating players in the sport.Since the flow of a baseball game has natural breaks to it, and normally players act individually rather than performing in clusters, the sport lends itself to easy record-keeping and statistics...

 is the earned run average

Earned run average

In baseball statistics, earned run average is the mean of earned runs given up by a pitcher per nine innings pitched. It is determined by dividing the number of earned runs allowed by the number of innings pitched and multiplying by nine...

 of the pitcher

Pitcher

In baseball, the pitcher is the player who throwsthe baseball from the pitcher's mound toward the catcher to begin each play, with the goal of retiring a batter, who attempts to either make contact with the pitched ball or draw a walk. In the numbering system used to record defensive plays, the...

s pitching when the catcher

Catcher

Catcher is a position for a baseball or softball player. When a batter takes his turn to hit, the catcher crouches behind home plate, in front of the umpire, and receives the ball from the pitcher. This is a catcher's primary duty, but he is also called upon to master many other skills in order to...

 in question is catching. Its primary purpose is to measure a catcher's game-calling, rather than his effect on the opposing team's running game. Craig Wright

Craig R. Wright

Craig R. Wright is a major proponent of sabermetrics, a baseball writer and historian.He was a very early pioneer in integrating science into major league baseball and first began working under that premise for the Texas Rangers, after the strike of 1981...

 first described the concept of CERA in his 1989 book The Diamond Appraised. With it, Wright developed a method of determining a catcher's effect on a team's pitching staff by comparing pitchers' performance when playing with different catchers.

However, Baseball Prospectus

Baseball Prospectus

Baseball Prospectus is an organization that publishes a website, BaseballProspectus.com, devoted to the sabermetric analysis of baseball. BP has a staff of regular columnists and provides advanced statistics as well player and team performance projections on the site...

 writer Keith Woolner

Keith Woolner

Keith Woolner is an author for Baseball Prospectus and is the creator of the runs-based statistic VORP or Value Over Replacement Player. VORP is acknowledged by the sabermetrics community as one of the key concepts in the analysis of a player's performance and market valuation.-Education and early...

 found through statistical analysis of catcher performance that "catcher game-calling isn't a statistically significant skill". Sabermetrician Bill James

Bill James

George William “Bill” James is a baseball writer, historian, and statistician whose work has been widely influential. Since 1977, James has written more than two dozen books devoted to baseball history and statistics...

, too, performed research into CERA, finding that while it is possible that catchers may have a significant effect on a pitching staff, there is too much yearly variation in CERA for it to be a reliable indicator of ability. James used simulations of catchers with assigned defensive values to directly compare CERAs, which influenced Woolner to perform similar simulations but instead using weighted events to calculate pitchers' runs per plate appearance. Through this, Woolner concluded that even if catchers do have an effect on pitchers' abilities to prevent runs, it is undetectable and thus has no practical usage. He also stated that "the hypothesis most consistent with the available facts appears to be that catchers do not have a significant effect on pitcher performance".