Since the Cubs announced earlier this year their hiring of noted sabermetrician Tom Tango (his nom de baseball, since his real name is a secret), it shouldn't be a surprise that run expectancy has been cropping up on the television broadcasts. These are three tables that can be found at this site that I've combined into one place for easy reference. This first table shows the average number of runs that can be expected to score given the various base runners and outs in an inning:
Don't be intimidated, it's much easier than it looks. The first line shows the bases empty and tells us that with the bases empty and 0 outs, a team can expect to score .544 runs by the end of the inning, .291 runs if there's one out and .112 if there's two. These are completely intuitive and don't require fancy math as much as the raw power (and extreme patience) to crunch through reams of data.
This next chart shows the numbers (or close to them) that the Cubs are showing on their broadcasts--they are the percentage of opportunities in which a run will score. It doesn't matter whether one run or ten scores, these numbers are the odds that a run will score:
Using the bases empty again, with 0 outs, a run (or more) will score 29.3% of the time, 17.2% of the time with 1 out and 7.5% of the time with two outs. Again, total common sense and the application of number crunching, but it's still nice to see what happens. For example, look at the last line--with the bases loaded and 0 outs, a run scored 87.7% of the time--that means in 12.3% of the time (around 1 in 8) a run DIDN'T SCORE in this situation--THAT'S amazing.
This last table is the percentage of times that these situations occur:
As you watch Cubs broadcasts or any other that is advanced enough to show these numbers, be sure to thank Tom Tango for doing this--all it does is take what we know (the fewer the outs, the greater the chance to score) and quantify it. Fancy numbers, if done correctly, explain more than confuse. Thanks, Tom Tango.