This post serves as a companion to a commentary post on the biased nature of expert opinion.
What if we treated the batting order of the 2012 San Francisco Giants like the Brookings Institution treated five equal groups, or quintiles, of American taxpayers?
Batting averages serve as a handy parallel. Most Americans are somewhat familiar with baseball. And the batting averages for teams are somewhat progressive. Players with higher batting averages tend to receive more opportunities to hit.
ESPN lists 45 Giants players in its batting stats for the 2012 regular season. Many of them had no hits at all, leaving them with .000 batting averages. To keep the stats more interesting, I only used the top 30 batting averages, leaving us with only two players at .000.
Divided into quintiles, the top six batters hit .318. The next six collectively hit .265. The middle quintile hit .226. The second quintile hit .156 and the lowest quintile batted .094. The batting averages for each quintile are stacked in a column in the accompanying graphic.
The “team batting average” for the 30 players in our sample came out to .269, but the batting average for the average batter was .205, a much lower figure. The procedure Greenstone and Looney used offers us .236 as the “average” taxpayer’s rate, by analogy. That “average” figure isn’t just 31 points higher than the average of the average Giants batter, it’s also 17 points higher than the median figure of .219, represented by Hunter Pence in our sample as number 15 on the list.
The three key averages occur as horizontal black lines on the chart.
Does the horizontal line labeled “P0-80” best represent the average batter? Let’s at least note that it does a better job of representing the average Giants batter than does the team batting average of .269.
There are times when it is much more appropriate in baseball to refer the team batting average than to the average achieved by the average batter. In like manner, legitimate uses exist for the P0-80 group average for federal taxes. At the same time, the multitude of figures provide rich potential for creating a misleading impression.