In my Box Score Ephemera post earlier today, I commented on how interesting it was that of the eight games (16 teams) yesterday, four teams scored three runs, and three won despite that low run total. Back in the day (which in this case means early 2011) I was trying to get my stuff published on the Community Research section of FanGraphs and was going to investigate this. The numbers ARE intriguing and enlightening, but displaying them--well, that's another matter. I'll try anyway, because messy charts can also tell a story.
There are two elements at work--the first being the number of runs scored and the second how often teams win scoring that number of runs. This first chart shows the number of runs scored per game by team from 1901-2012:
Once you clear your eyes, you'll see a pretty clear pattern. In this time span, we can see that teams are shut out somewhere in the 5-10% range, score one run at a similar rate, with the percentages all adding up to 100%. This chart summarizes the win percent:
In this 100+ year time span, the number of runs scored per team has held pretty steady at around 4.5 runs a game, and these numbers bear that out. The win percent jumps from .397 with three runs scored to .533 at four, and moves up steadily after that. In order to add perspective, winning at a .600 clip is equivalent to a 97-65 rate, and in a five-team playoff format, that virtually guarantees a slot in the playoffs (I think I've done the research, but I can't remember if I published it here--wait, it's right here).
I typically cut off runs at six, but broke it out to ten in this case, even though it's apparent that scoring that many runs usually guarantees victory. The problem with this table is that it is NOT the same over time. You can see the fluctuations in the first chart, which is why I included it.
Baseball can be broken into these (completely arbitrary) eras:
1901-1919--The Deadball Era
1920-1960--The Lively Ball Era (some people break out World War II--good for them)
1961-1968--The Mini Deadball Era
1969-1994--The Expansion Era
1995-2006--The "Enhanced Offense" Era (a case could be made to extend this to 2007)
2007-2012--The Current Era
This table breaks out these values by era:
In the Dead Ball Era, teams scoring one run won almost 16% of the time. That fell quickly after 1920, but a noticeable dip did occur in the Mini Deadball Era. The real differences come out at the four run line, where teams won 59% of the time in the Dead Ball Era, which was reduced to 47.4% of the time in the "Enhanced Offense" Era and is back to the historical norm of around .500 now. Any columns of percentages that don't add up to 100 are due to rounding errors.
The change from the "Enhanced Offense" Era to the current game isn't as dramatic as the shift from the Dead Ball Era, and the rash of new stadiums built from 1991 on is extremely important in the increase in offense, but it's obvious that a change in offense has occurred. There's a 9.2% increase in the teams winning when scoring 5 runs, and the difference between the four and five run winning percents is as great as it's ever been. Better pitching? Perhaps--it HAS to play some kind of factor. Smaller parks? Absolutely. Better hitters? Of course--players are in the best shape ever and spend 12 months a year working on their game. These factors can work at cross purposes, but there's an across-the-board increase in winning percentage at every run level, which means that fewer runs are needed to win a game than even five years ago.
This last chart is a mess, but it's like the first one--there's a story in the middle of it:
Any similarity between this and Joy Division's first album cover is purely coincidental. The line to watch is the 4 Run line (blue) and observe how it fluctuates over the years, with a very significant uptick beginning around 2007. This is how three of four teams that scored three runs in their games yesterday can win--it's a different day.