BABIP and You: A User’s Guide, Part 1

Batting average on balls in play, BABIP — one of the simplest baseball stats, and one of the most powerful. In the past few weeks, I’ve seen a couple of questions about BABIP and its uses, and I thought it was worth writing about. If you’ve ever wondered what it all means — BABIP, that is, not life in general — read on. I’ll try to explain the best way I know how: By talking to myself.

Flood: BABIP, BABIP, BABIP. All right, I see this all over the internet, so tell me — what’s BABIP, exactly?

PJF: BABIP stands for “Batting Average on Balls In Play.” It’s exactly what it sounds like it is.

Flood: Oh, of course. So simple. I guess we’re done here

Twiddles thumbs, nods knowingly, stares at the wall . . .

But just in case someone else doesn’t know, it’s . . .

PJF: Batting average on balls that are put into play — so a batting average ignoring home runs and strikeouts. Everything else is a ball in play. The formula for regular old batting average is:

hits
divided by at bats

The formula for batting average on balls in play is:

(hits minus home runs)
divided by (at-bats, minus home runs, minus strikeouts, plus sac flies)

It’s batting average on balls that could conceivably be fielded by the defense.

Flood: Okay, that’s simple enough, BABIP is batting average without home runs and strikeouts. Why on earth should I care about this?

PJF: Do you play fantasy baseball? Do you play real baseball? Are you Bobby Parnell? Or do you like making simple predictions about baseball players that generally prove correct and make you seem more intelligent and attractive in the eyes of your loved ones?

Flood: No; not anymore but I’m dangerous pull hitter in wiffleball; possibly; and yes.

PJF: Than you want to know about batting average on balls in play (which we abbreviate as BABIP). Because it can tell you which players are over their heads and which ones are going to get better.

Here’s the deal: There are a few constants throughout all baseball history. The distance between the bases in 90 feet. Nine men per side. Three outs make an inning, you play nine innings unless it rains or gets too dark. Vin Scully. And the league’s batting average on balls put in play, the BABIP, is around .280-.300.

That last ones sounds strange, but it’s true. The number of runs scored per game, the number of home runs, the number of triples – these things have changed all throughout baseball history. Teams score 4.15 runs per game in the National League this season . . . but in 1930, NL teams scored 5.68 runs every game and in 1968 they scored 3.48 runs every game. Errors have been decreasing throughout all baseball history and strikeouts have been increasing. There have been seasons where .309 is a normal batting average, and seasons when .248 is a normal average. Parts of the game change as baseball evolves.

But not every part of the game changes. In 1900, the National League batted .295 on balls put in play; in 2010, the NL batted .299 on balls put in play. Going decade by decade: In 1910 the league BABIP was .283, then .290 in 1920, .318 in 1930, .280 in 1940, .275 in 1950, then .280, .287, .286, .286, .298 in 2010. There are some years when it’s higher and some when it’s lower, but for most of baseball history, whenever a batter puts a ball into play, he’ll end up with a base hit 28-30% of the time.

Flood: All right, but what people were doing in 1900 is relevant now because? You know Queen Victoria was still alive then, right? And The Kinks wouldn’t write a now-42-year-old song about her for another 69 years.

PJF: It’s relevant because that’s over 110 years of evidence that suggests a .280, .290 BABIP is in the nature of the game.

Flood: Oh, good, thanks, I’m totally ready to win my fantasy baseball league now . . .

PJF: Here’s where it gets interesting, or at least where it can help you win your league. Or something. Batting average on balls in play varies wildly from season to season. Among the ten hitters who led the majors in BABIP last season, none of them are in the top ten this season. Only one (Joey Votto) is even in the top 30. Among the ten pitchers with the lowest BABIP against in 2010, none of them have one of the ten lowest BABIP again this season. Compare that with something like home runs — six of the top 10 home run hitters from last season are in the top 10 in home runs again this season — or stolen bases, ERA or strikeouts, categories in which the same players lead the league season after season.

Think about it: If certain players perform well in a category one year, and then those same players perform well in that same category again the next season, and the season after that, does that category indicate a skill or luck? Because that’s what you see with home runs, stolen bases, ERA. The same names on top of the leaderboard season after season.

But if certain players perform well in a category one year, and then an entirely different group of players leads in that category the next year, and then an entirely new group the season after that – is that category measuring a skill? Because that’s how BABIP works. Different names are all over the leaderboard every season.

Flood: So you’re saying that even season to season, for the same player, BABIP varies wildly? Even for good players?

PJF: Pedro Martinez was a pretty good pitcher, right? And . . . oh, shoot, hold on. We’re at the end of Part 1. We’ll keep going in Part 2 a little bit later. There’s still plenty more.

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2 Comments

Filed under Columns, Words

2 responses to “BABIP and You: A User’s Guide, Part 1

  1. Good stuff so far, Patrick.

    Maybe you hit this later on, but BABIP is not just about luck or regression. In some cases, a low BABIP is about luck but in others it is a signal that something has changed with the batter. It might be approach at the plate, it might be a change in swing or injury, or it may signal that the player is simply ageing.

    Low BABIP alone can’t tell you if a batter is just unlucky. It does tell you that you need to check a few more places first before making a determination (e.g. batted ball profile, plate discipline, etc).

    Also, a high BABIP might be luck but it might also be reflective of player skill. There are some players with consistently higher BABIPs. You’d have to look at their current BABIP in the context of their career before saying their are set to regress.

    Like I said, you might be hitting this in the later posts.

    Looking forward to the next two parts.

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