The Era of Encroaching Dinger Reliance

Back in 2014, the average baseball team scored 4.07 runs per game. That was down only a tenth of a run from the year before, which was down only a little more than a tenth of a run from the year before that, but a definite trend was emerging. An average of 4.07 was the league’s lowest mark since 1981, and there were gathering concerns that offense was being suffocated. No one really knows how low is too low, but Rob Manfred considered various ideas that might re-inject some hitting. This is why conspiracy theories persist to this day.

Rather conveniently, see, offense bounced back in 2015. It surged again in 2016, and it’s surged only more over the past five months. The average team now is up to 4.68 runs per game, which feels more familiar. The surge has been powered by a well-publicized and well-examined home-run spike, but at the end of the day, offense is offense, right?

It is, and it’s good that hitters again have a chance. The balance of power had felt like it was shifted too far. But in a certain sense, you could argue that this offensive surge is artificial. For a variety of reasons, home runs are up, and they’ve gone up right when they needed to. But offenses now are so very home-run reliant. Everything to follow is probably obvious, but I might as well explicitly lay it out. Home runs are taking over the game.

For some of you, this’ll be review. Or, if not review, it’ll cover trends you already assumed. Let’s go back to 1950. Here is a simple plot, of the rate of home runs per plate appearance, league-wide:

Yeah, there’s been a home-run spike. You know that, and your neighbors know that, and your neighbors’ children know that, and your neighbors’ children’s pets know that. But keep in mind this isn’t a plot showing home-run rate on contact. This is home-run rate, overall, and even despite the league-wide increase in strikeouts, we’re at a relative maximum. The highest rate in the sample belongs to 2017. The second-highest rate in the sample belongs to 2016. There’s less contact than ever, but there are more home runs than ever. The difference is made up in the following plot.

This shows the yearly rates of time-on-base events, excluding home runs. So it’s a combination of singles rate, doubles rate, triples rate, walk rate, and hit-by-pitch rate. Another pattern emerges:

The league isn’t presently anywhere ultra-low, but there’s still an obvious dip, relative to the previous few decades. This is a consequence of the strikeout spike. Those strikeouts have to eat away at something, and they’ve eaten away at non-homers. As a consequence of both of the trends imaged above, you can see that runs are being distributed differently.

This shows average runs per game scored on homers, and average runs per game scored on non-homers. You see that the lines are going in different directions.

With 1.99 runs per game scored on homers, that line is at its highest point. But then, there have been just 2.69 runs per game scored on non-homers, and that’s the eighth-lowest point in the sample of 68 seasons. You can observe that the red line has kind of flattened out. Although league-wide offense is climbing back up, it’s entirely because of the longball. As another way to visualize that, we can combine these numbers into one.

Enter the Guillen Number, a measure initially created by Joe Sheehan several years ago. The Guillen Number is simple. The denominator is all runs scored. Just plain overall runs. The numerator is runs scored directly on homers. How reliant is the league on home runs these days? The trend is unmistakable.

Again, we’re looking at 68 seasons. The third-highest Guillen Number came in 2015, when the league finished at 37.1%. The second-highest Guillen Number came in 2016, when the league finished at 40.1%. The single highest Guillen Number for now is happening in 2017, with the league sitting at 42.6%. In other words, about 43% of all runs are being scored on homers. That’s three out of every seven. While it might not feel like the league is yet all that close to 50%, consider that it was at 33% as recently as 2014. Since then, the Guillen Number has increased by about 10 percentage points. Home runs are taking over team offense. I think most of you already knew that, but perhaps you hadn’t considered it like this.

Because I’m here, I might as well show you what this year’s team-by-team breakdown looks like. Try not to stare too long at the Giants.

The Blue Jays have scored 51% of their runs so far on homers. They’re the only team at something greater than half, but the Rangers are awfully close. More meaningfully, there have been 1,682 individual team-seasons since 1950. Five of the 10 highest Guillen Numbers are getting put up right now, in 2017. There are an additional three teams from 2016. The highest mark so far belongs to the 2010 Blue Jays, who finished at 53.1%. No one right now is threatening to depose them from the throne, but the league is moving forward as a collective. Again, this year’s league Guillen Number is 42.6%. Three years ago, there was just one team that topped that.

This isn’t inherently a good thing or a bad thing. It’s a matter of taste, and some people like movies for the dialogue, while other people like movies for explosions. Neither group of people is superior to the other, and taste feels like a silly thing to criticize. Just, understand what is presently going on. Offense is back, relative to a few years ago, but that’s happened entirely because of the home run. In the run-production pie chart, the home-run slice is getting wider and wider. Runs aren’t back because of anything else. Manufacturing a run isn’t suddenly back in style. Teams now manufacture their runs with big mighty hacks, and trying anything else can feel borderline futile. Home runs aren’t everything, but they’re closer than they’ve ever been. What that means to you is personal, but it’s something for each of us to grasp.