Batting Average on Balls in Play, or BABIP, is a measure of a hitter’s batting average on batted balls that can be fielded (thus are “in play”). It would include all ground balls, line drives, fly balls (including sacrifice flies), and fielded foul outs. It does not include at bats where the batter strikes out or hits a home run (the ball is not put “in play” during these at bats).
For example, assume a player has 10 at bats. Within those ten at bats the player strikes out three times and hits one home run. That leaves six balls that were batted in play (10 at bats – 3 Ks – 1 HR = 6 balls in play). Of those six balls in play, two were for hits and four were various outs (ground outs, fly outs, etc.). In this example, the player’s BABIP would be .333 (2 hits / 6 balls in play).
The official formula for BABIP is:
BABIP = (H – HR) / (AB – K – HR + SF)
WHAT IS THIS STAT TRYING TO ACCOMPLISH? WHAT DOES IT TELL ME?
On a very simplistic level, BABIP is a measure of a batter’s luck. The theory is that a player’s skill contributes significantly to their contact rate (avoiding strike outs) and hitting for power (home runs), but there are other factors (like luck, which is beyond the hitter’s skill or control) that come into play when a ball is batted into play.
When a player hits a hard line drive they may be unlucky and have it hit directly at an opposing fielder. Or a player may be lucky and hit a soft blooper over the infield.
Figure 1 below shows the BABIP for all hitters with at least 250 ABs for the last five years. You can see that BABIP hovers consistently around the .300 – .305 mark.
Figure 1 – BABIP for All Hitters with >250 AB
ARE THERE ANY WEAKNESSES IN BABIP?
I think the main weakness is simply its misuse. It’s not uncommon to see fantasy baseball analyst comments like, “Player A has a BABIP of .340, he’s been extremely lucky. That’s got to come down at some point.” The thought being that Player A’s BABIP must fall to around .300, the league average. This is flawed logic!
It is interesting to view actual batting averages with BABIP in mind, but it’s too simplistic to assume all hitters should have a .300 BABIP. Faster players have proven to have higher BABIP due to their ability to beat out more infield hits. A look at the names in Figure 2 below would seem to support this statement (errr, ignore the three catchers in the top 10).
Figure 2 – BABIP Leaders for 2012
And it’s not just fast players that can post a high BABIP. Many players can consistently post BABIP greater than .300, indicating that a hitter’s skill (and not just speed) can have a significant effect on the number. A list of players with the highest BABIP since 1980 (and more than 5,000 plate appearances since 1980) are shown below.
Figure 3 – Highest Career BABIP Since 1980, min 5,000 PAs
WHY SHOULD I CARE ABOUT BABIP Then?
I’ll call BABIP a building block stat. It’s something we need to get to a more powerful statistic – Expected BABIP (xBABIP).
What do you think?
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- Fangraphs definition
- Yahoo!’s Big League Stew
- ESPN’s Tristan Cockcroft (Great read. I wish I had found this earlier… didn’t stumble upon it until this post was nearly completed)
- Statistics courtesy of Fangraphs