I thought it'd be interesting to see if there was any difference between clubs' MLB rank by earned runs and runs. As most of you know, errors are out of vogue in fielding statistics for a variety of reasons. Scorer bias and subjectivity is one of them. If a Safeco scorer gives Ichiro a hit when the second baseman actually committed an error, and Ichiro comes around to score, that run is earned. Perhaps the exact same chain of events happens in Toronto, for example. Unearned run. Combine subjectivity with the fact that errors really aren't a very good gauge of defence, and you start to see looking at earned runs doesn't actually tell you how many runs a team's given up on the year. Case in point:
Table 1: 2009 Runs, Earned Runs, and MLB ranks. All data from Baseball-Reference.
Green denotes that the team was over-rated by using ERA, red denotes them being under-rated. Interesting, huh? Scanning that chart, I'm not seeing any correlation between green/red teams and actual defensive ability (and with this being a quick post I'm not inclined to dig too deep). I just thought it was interesting that although we can generally multiply ERA by 1.087 to get RA, that relationship doesn't even hold true at the team level. Note that only six teams don't see their rank change - the Mariners are one of them, holding steady at sixth in both categories. The most underrated team is the Minnesota Twins, who go from 25th by earned runs to 19th by runs, and at the opposite end of the spectrum we have the Florida Marlins, who tumble from 14th to 20th.