Keep leads in each inning in 2007

Taken from the Baseball-Reference.com Play Index Team Inning Summary, here is a graph of the 2007 performance at all teams keeping leads each inning.


What this tells you, for example, is that when a team entered the second inning with a lead, it kept that lead through the end of the second inning almost 85% f the time in 2007. For the second inning, the actual data was 1063 out of 1254 second-inning leads retained (84.8%)

As the innings go on, the number of leads increases. For example, teams entered the third inning with a lead 1636 times in 2007 (as compared to 1063 second-inning leads,) and retained those leads 1436 times (87.8%.)

Something wacky happened in the fourth inning, though. Those leads weren't as safe. Teams entered the fourth inning with a lead 1904 times, but kept them just 1630 times (85.6%.) Now, this is based on an awful lot of leads, so it's very unlikely to be a statistical anomaly (more on this below.) My guess is that in 2007, the fourth inning saw the top of the lineup come up to bat again a bunch, and this group was able to erase the deficit more often than the bottom of the order could do it in the third inning.

From innings 5 through 8, there was a steadily proportional increase in the lead being retained each inning. Then in the ninth inning, we saw an extra bump up to 93.4%. I assume this bump is due to the use of closers who are good at retaining leads, or at least better than the middle- and late-inning relievers often pitching in the 6th, 7th, and 8th innings.

I went ahead and calculated the same data for 2006 and 2005 as well, and added them to the graph:


So it's the same 2007 data (blue) plus 2006 data (yellow) and 2005 data (green.)

The 2006 data looks pretty similar to the 2007 data, with a drop in the 4th inning, pretty much a steady increase in innings 5 through 8, and then an extra bump in the 9th, keeping those leads safe.

The 2005 data is fairly wacky, though. It shows that there were more rallies in the 3rd inning, and also more rallies in the 6th inning as compared to the 5th. In fact, you notice that even in 2006 (yellow) the 5th and 6th innings were quite comparable. The 2005 data also shows a 9th-inning bump.

What's going on here? Well, it's complicated. I am guessing that the unusual behavior has to do with the size of the leads.

If this data looked only at 1-run leads, then we'd expect it to be very flat in innings 5 through 8. In other words, it's pretty much as easy to lose a 1-run lead in the 5th, 6th, 7th, or 8th innings. But in reality, as games go on, leads tend to get larger. In other words, it's much more like for a team to have a 3-run lead in the 8th inning than it is in the 4th inning. So, on average, an 8th inning deficit would be harder to overcome than a 4th-inning deficit (since it's larger.) But, from year to year, even with 1000-2000 games at play, there are variations. Some years, those later leads are smaller, or early leads are bigger, or teams hit better or worse with runners in scoring position, for example.

So what are the take-home messages?

• Closers do seem pretty effective at retaining 9th-inning leads.
• Teams that enter the 2nd inning with a lead retain that lead by the end of the 2nd inning about 85% of the time.
• Teams that enter the 9th inning with a lead retain that lead by the end of the 9th inning about 93% of the time.
• What happens in between is a roughly linear trend, but it varies from year to year.