4 Pros and 4 Cons of Using ERA as a Statistic

ERA stands for “earned run average” and it represents the number of earned runs that a pitcher allows per nine innings. A pitcher’s ERA is one of the many statistics that baseball fans can use to judge how well a pitcher performs because it is the most well-known and accepted statistic for analyzing pitchers, but on occasion, you’ll hear fans complain about using ERA to judge pitchers. So, is ERA a good stat?

As a general rule, ERA is a good statistic to judge a pitcher’s performance, but ERA should also be used with other statistics to help determine how well a pitcher has performed. A pitcher’s ERA is the most common way to judge how well a pitcher is doing.

While it may be common for ERA to be considered a good statistic, many people believe the statistic is flawed. In this article, we’ll cover four pros and four cons of using ERA as a statistic in baseball. By the end of this article, you’ll be in a better position to determine whether or not you think ERA is a good statistic to use.

Learn more about what is an ERA by reading A Beginner’s Guide to Baseball’s ERA Statistic.

4 Pros of Using ERA as a Statistic

1) ERA is a Widely Accepted Stat

An ERA is one of the most traditional and commonly used statistics for baseball pitchers. It has been ingrained into baseball analysis for quite some time. Many fans are both comfortable and familiar with this statistic, as it is a statistic that is shown at every baseball game.

Even though other ways of measuring pitchers have been introduced, discussed, and used, most analysts and writers still use ERA in their discussions.

2) ERA is Easy to Understand

The concept of ERA is great on its own. In general, an ERA number evaluates how well a pitcher does over a time frame of nine innings. The lower the number, the lower number of runs a pitcher gives up per nine innings.

Additionally, this calculation uses established rules that try to filter out external factors that are out of a pitcher’s control, such as runs that were scored with the help of an error, passed ball, etc. Although sometimes it isn’t so easy to know what is an earned run. Read about what makes a run an earned run to learn more about what type of runs count towards a pitcher’s ERA.

As a general rule, the lower a pitcher’s ERA, the better they are. The idea and intentions behind using ERA are solid and have the potential to be very effective.

3) The Method For Calculating ERA Doesn’t Change

ERA is a calculation that doesn’t change very often. In fact, there are only 3 steps to calculating a pitcher’s ERA. This means that it is a lot easier to compare a pitcher from today to a pitcher from 10 years ago or more. This also means that it is a lot easier to compare a pitcher on one team to a pitcher on another team.

An ERA number evaluates the effectiveness of pitchers by dividing the number of earned runs by the number of innings pitched, and then multiplying that number by nine (which is the number of innings in a baseball game).

One way the calculation of ERA could change is if baseball changed what determines an earned run and what determines an unearned run. However, those rules very rarely change, which means the way to calculate ERA very rarely changes.

4) ERA Filters Out Defensive Mistakes

The statistician who created ERA really tried to maximize data accuracy by considering and accounting for external errors that are not a reflection of the pitchers’ ability. If there is a run made that only occurred due to an external, uncontrollable error, it makes sense that they wouldn’t want it to count against the pitcher.

Using this type of calculation helps players, fans, and coaches determine a pitcher’s ability by not factoring in those runs where errors occurred. A lower ERA number typically means a pitcher has a lot of ability to get outs on their own.

4 Cons of Using ERA as a Statistic

1) Other Statistics Are More Accurate

ERA attempts to remove the pitcher’s accountability for extraneous events that might influence the calculation of earned runs. That being said, some people prefer to know how many runs a pitcher gave up, regardless of their defense, while others simply want to know the effectiveness of a pitcher, regardless of how their defense performs.

Runs Allowed Per Nine Innings Pitched (RA9) and Fielding Independent Pitching (FIP) also calculate the effectiveness of a pitcher.

RA9 is simply the number of runs allowed per nine innings, regardless of whether those runs were earned or unearned.

FIP is a number that only takes into account the plays the pitcher has the most control over, like strikeouts, walks, etc. If a ball is hit in play, that play is not accounted for in FIP.

ERA has been described to be biased and inaccurate because it produces a skewed viewpoint, but RA9 and FIP can also be used to determine a pitcher’s effectiveness.

2) ERA Doesn’t Soley Focus on a Pitcher’s Ability

One common reason ERA is viewed negatively is because there are so many factors that influence this statistic, with the biggest factor being how well a defense plays. When a pitcher has a poor defense behind them, they tend to give up more earned runs.

Another factor is that relief pitchers don’t pitch to the same players as starters. Some relief pitchers may only go in for a batter or two because they have a favorable matchup, which means these relief pitchers would end up with a lower ERA.

These factors generally decrease people’s trust in ERA as a statistic because there are many determinants that can influence this number.

3) Bias on Earned Runs vs Unearned Runs

There is not a clear and stable consensus as to what makes a run earned or unearned. In general, an earned run is any run the offense scores without the help of an error or a passed ball, but it’s up to someone to determine whether or not a certain play is an error.

This alone instantly increases the margin of error because some people may consider a play an earned run while others would consider it an unearned run.

People argue that if there is no established consensus for the foundation of what makes something an earned run, then the ERA is a flawed statistic.

When we focus on earned runs as opposed to all runs the pitcher allowed to happen, we are making a statistic based on a personal judgment. And it’s more difficult to compare pitchers to one another when the statistic being used is based on a personal judgment.

4) Number of Innings Pitched

One important piece of data needed to calculate ERA is the number of innings pitched. However, the problem many people have with this is that starting pitchers and relief pitchers do not come close to pitching the same number of innings, especially when you factor in specialty pitchers like set-up pitchers and closers.

For example, if you look at the statistics I threw up in my previous article about what is a good ERA in baseball, you’ll see that during the 2021 season, starting pitchers threw a total of 24,402.1 innings while relief pitchers threw a total of 18,212.2 innings. That means starting pitchers threw 6,189.9 more innings than relief pitchers in the 2021 season.

Even though starting pitchers throw a lot more innings than relief pitchers, they both calculate ERA by using the number of innings pitched.

Another issue people run into is when a pitcher gives up an earned run, but technically pitches no innings. This leads to something called an infinity ERA, which some find to be a very unhelpful stat. Read more to learn how to get an infinity ERA in baseball.

A third issue with using the number of innings pitched is that starting pitchers will see the same batters multiple times in a game (typically 2-3 times a game) while relief pitchers will see each batter only once. This means that the second or third time a batter encounters a pitcher, they are more likely to be able to get on base and score runs.

A final advantage that relief pitchers have when it comes to using ERA is that they very rarely pitch most of the innings in a game. So fans will argue that comparing someone who only had to pitch for let’s say, 30 minutes, to someone who has been pitching for 2 hours doesn’t seem fair at all.