The Prince is King of the long ball.

The end of the 2007 season is rapidly approaching, and there are two statistics worth noting that you might have missed. One is probably something you have noticed – home runs are down across the major leagues. The second is something you probably missed – the National League has reversed a long-standing trend and hit more home runs than the American League. In other words, the heroics of Prince Fielder and friends have surpassed those of Alex Rodriguez and his compatriots in terms of power production.

This week, I will be looking at aggregate home run numbers and how they are normalized. If normalization sounds a bit scary to you (a bit nonconformist, perhaps?) don’t worry, I will get through it without scaring you too much. The first number I want to talk about is a simple one: HR/100, or home runs per 100 at-bats. Why 100 at-bats? It’s a nice round number, it works out to roughly the number of at-bats a full-time player should get per month, and it makes a statistic like HR/100 a lot easier to work with.

For the 2007 season (through Tuesday’s games), the average National League team hit 164 home runs in 5,420 at-bats. That gives them a HR/100 of 3.03 [(164/5420)*100] which ranks ahead of the American League (HR/100 of 2.87). Previously, the AL had outpaced the NL every year from 2003-2006, and I suspect that they had also dominated for several seasons beyond that range. The overall HR/100 for major league baseball in 2007 is 2.95, which marks the first time in five seasons that it has been below 3.00 (3.13 in 2003, 3.26 in 2004, 3.01 in 2005, and 3.23 in 2006). What does this mean? Home runs are down about 8.7 percent in 2007 – draw your own conclusions about the reasons, because that could fill a book instead of a column.

The decrease in home runs has been particularly evident in the AL: 11.7 percent fewer home runs than the 2006 season. So if you are wondering what happened to Travis Hafner, remember that it isn’t entirely his own fault, but I’ll pick on him anyway as a way to introduce the idea of normalization. In 2006, Hafner hit 42 home runs in 454 at-bats, giving him a HR/100 of 9.25 for the season. The average American League hitter swatted 3.25 home runs per 100 at-bats, so Hafner hit 2.85 times more HR/100 than the average hitter – or 285% of the average total. This total of 285% is what I call normalized: compared to the average hitter. You will sometimes see statistics like this on sites like baseball-reference.com with a “+” next to the statistic – ERA+, OPS+, etc – so I will refer to this statistic as HR/100+.

(Warning: tangent alert. If home runs were evenly distributed, we could plot Hafner’s mark of 2.85 standard deviations above the mean on a normal plot and find out that he was above the 99th percentile, but that’s another column and since home runs aren’t anywhere close to normally distributed, it isn’t really helpful for fantasy baseball, so I will skip it.)

Despite his struggles this season, Hafner has hit a respectable 23 home runs in 529 at-bats, giving him a HR/100 of 4.35. That gives him a normalized HR/100 (HR/100+) of 151. Hafner has still been 50 percent better than the average hitter, but that is a far cry from last year when he was almost 3 times as good. So, while the drop in home runs around the AL explains some of his decline, it still hasn’t been a very good year. Hopefully by now you know how to check indicators like HR/FB%, groundball ratio, BABIP, and other key statistics to investigate Hafner’s decline further.

So, getting back to Prince and A-Rod, who has been better compared to their league this year? Rodriguez has more home runs in a tougher league, so it should be him, right? Correct. A-Rod has a HR/100+ of 322, compared to “only” 294 for Fielder. Last year’s leaders in HR/100+ were David Ortiz (298) and Ryan Howard (311), so Rodriguez is clearly having a season for the ages. Hafner ranked second in the AL last year at 285, and Albert Pujols ranked second in the NL at 286. In all, 22 players topped 200 HR/100+ last season, including 13 from the NL and 9 from the AL. This year, 14 players have topped that mark, 8 from the AL and 6 from the NL. I have included the top 10 from each league for the 2007 season below. What does it all mean? A-Rod is really, really good. You probably didn’t need to read this column to figure that out, but now you know another reason why.

American League Top 10 HR/100+ in 2007:

National League Top 10 HR/100+ in 2007:

Questions and comments may be sent to johnfranco@sportsgrumblings.com