Adjusted ERA+

Adjusted ERA+, often simply abbreviated to ERA+ or ERA plus, is a pitching statistic in baseball. It adjusts a pitcher's earned run average (ERA) according to the pitcher's ballpark (in case the ballpark favors batters or pitchers) and the ERA of the pitcher's league. Average ERA+ is set to be 100; a score above 100 indicates that the pitcher performed better than average, below 100 indicates worse than average.

For instance, if the average ERA in the league is 4.00, and the pitcher is pitching in a ballpark that favors hitters, and his ERA is 4.00, then his ERA+ will be over 100. Likewise, if the average ERA in the league is 3.00, and the pitcher is pitching in a ballpark favoring pitchers, and the pitcher's ERA is 3.00, then the pitcher's ERA+ will be below 100.

As a result, ERA+ can be used to compare pitchers across different run environments. In the above example, the first pitcher may have performed better than the second pitcher, even though his ERA is higher. ERA+ can be used to account for this misleading impression.

Pedro Martínez holds the modern record for highest ERA+ in a single season; he posted a 1.74 ERA in the 2000 American League, which had an average ERA of 4.92, which gave Martinez an ERA+ of 291.^[1] While Bob Gibson has the lowest ERA in modern times (1.12 in the National League in 1968), the average ERA was 2.99 that year (the so-called Year of the Pitcher) and so Gibson's ERA+ is 258, sixth highest since 1900. 1968 was the last year that Major League Baseball employed the use of a pitcher's mound greater than 10 inches.^[2]

The career record for ERA+ (with a minimum of 1,000 innings pitched) is held by Mariano Rivera, a closer who has a career ERA+ of 206. The career record ERA+ amongst retired players is 154, held by Pedro Martinez, with Jim Devlin, a pitcher in the 1870s, next at 151.^[3] Pedro Martínez has the most separate seasons with an ERA+ over 200, with five, and the most consecutive 200 ERA+ seasons (4). Roger Clemens topped a 200 ERA+ three times, and Greg Maddux had two such seasons.

Leaders

Players in bold are active as of the beginning of the 2012 season and have not announced their retirement.

References