The Early Trend of 2013: Dingers!

It’s April 10th. Most teams have played eight games out of 162, or about 5% of their season schedule. You know it’s early. I know it’s early. Data from a little over a week of baseball is highly suspect, which is why you’ll see things like Coco Crisp with an .829 slugging percentage or Vernon Wells with a 206 wRC+. Over these kinds of samples, any player can look great or horrible. Even at the team level, the numbers don’t tell you much of anything.

However, there is one set of numbers that stabilize very quickly – overall league averages. While the variance among players and teams is large, early season data at the league level is actually highly correlated with overall seasonal averages, for pretty much any major number you want to look at. For instance, here’s April 2012 data compared with 2012 overall data for many of the pitching metrics we look at regularly here on FanGraphs:

2012	IP	BB%	K%	HR/FB	BABIP	LOB%	ERA	FIP	xFIP
April	6042.2	8.2%	19.3%	10.5%	0.286	73.1%	3.84	3.98	4.09
Total	43355.1	8.0%	19.8%	11.3%	0.293	72.5%	4.01	4.01	4.01

HR/FB and BABIP were a little lower than the seasonal totals, but that’s normal, since April is the coolest month of the year, and the ball flies a bit better in the warmer summer months. Run scoring is usually lowest in April due to these factors, but beyond that minor adjustment, you can generally predict overall seasonal league run environment from April run environment with a pretty high degree of accuracy.

Since we’re only a little over a week into the season, we don’t have 6,000 innings of data yet. But, we do have 2,000 innings of data, and while they’re not as predictive as the full month will be, it is interesting to see how quickly these numbers have settled into something resembling a pretty normal overall league average line. Here’s that same chart as above, just for the first 116 games of 2013.

Season	IP	BB%	K%	HR/FB	BABIP	LOB%	ERA	FIP	xFIP
2013	2068.1	8.2%	20.2%	11.8%	0.289	72.0%	4.13	4.13	4.13

Walk rate is exactly where it was last year, and right in line with historical norms. Strikeout rate is up again, but it’s been aggressively trending upwards in recent years, and so that follows a pattern that we expected to continue. BABIP and LOB% look totally normal for this time of year. There are two numbers that are probably a bit higher than we would have expected, though, and they’re definitely related.

The league average ERA is 4.13 despite the increase in strikeouts for one simple reason; Major League teams have hit a lot of home runs in the first week of the season. Given the time of year we’re talking about, it’s almost an extraordinary amount of home runs.

During the 11 full seasons we have batted ball data from Baseball Info Solutions, HR/FB rate has never been higher than 11.3%, and that’s full season data. Here are the HR/FB rates for April over the last 11 years, along with that season’s total HR/FB rate and the gap between those numbers.

Year	April HR/FB	Season HR/FB	Difference
2002	9.7%	10.7%	1.0%
2003	10.9%	11.2%	0.3%
2004	11.1%	10.9%	-0.2%
2005	9.4%	10.6%	1.2%
2006	11.3%	10.8%	-0.5%
2007	8.8%	9.6%	0.8%
2008	9.0%	10.1%	1.1%
2009	10.1%	10.1%	0.0%
2010	9.6%	9.4%	-0.2%
2011	9.1%	9.7%	0.6%
2012	10.5%	11.3%	0.8%
Average	10.0%	10.4%	0.4%

Worth noting that April HR/FB rate has been higher than the season total in three of the 11 years we have batted ball data, so it’s not a hard and fast rule that HR/FB rate always increases throughout the summer. That said, it is true more often than not, and the overall average has put the increase at around half a percent. If teams kept hitting home runs at the same pace that they have so far, it would be the highest April HR/FB rate in the years that we have the data.

However, it gets even more interesting if we shift away from HR/FB and look at homers on contact. Since there’s a bit of a fine line between fly balls and line drives, HR/FB can be slightly affected by the categorization of balls hit in the air. If we really just want to look at a metric for measuring power, HR/CON is probably a better option.

I wrote about the HR/CON trend in baseball last summer, and noted that once you controlled for the rise in strikeouts, the rate of home runs last season was as high as it was during most of the “steroid era”. It didn’t quite reach the peak levels of the 1999-2001 stretch, but power definitely made a bit of a comeback last year.

It’s too early to call this a continuation of that trend, but I will note that the current MLB HR/CON rate in 2013 is 4.0%, the same as it was during the 1999 and 2001 seasons. Yes, it’s 116 games out of 2,430, and this could end up being nothing more than a blip on the radar, so don’t go overboard with any conclusions just yet.

However, April is supposed to be the month where the ball flies the least. The first week of April is the coldest weak of the month, on average. Because we haven’t even taken two full turns through the rotation yet, the innings totals are skewed towards each team’s best pitchers. And yet, despite all those variables that would theoretically push home run totals down, the ball is flying out of Major League stadiums at about the same rate it did during the absolute peak of the home run boom.

It could very well be nothing. 2,000 innings isn’t enough to draw any real conclusions. Maybe it’s been unseasonably warm the first week. With samples this small, a few gusts of wind and some random variation could be tricking us into seeing something that isn’t there. With that caveat, though, it is still something to keep an eye on. MLB saw an uptick in power last year, and it’s seen a very small sample uptick in power to start 2013. The rising strikeout rates are keeping the scores down enough to where it has gone unnoticed, but dingers might be making an underreported comeback in Major League Baseball right now.