|Composite Run Expectancy By Out and Baserunners|
|Situation||0 outs||1 out||2 outs|
|Man on 1st||0.896||0.535||0.227|
|Man on 2nd||1.149||0.697||0.333|
|Man on 3rd||1.395||0.969||0.365|
|1st and 2nd||1.505||0.922||0.458|
|1st and 3rd||1.776||1.188||0.505|
|2nd and 3rd||2.020||1.422||0.581|
Assuming equal weight to each season's run expectancy totals, the above chart utilizes a somewhat arbitrary 50-30-10-6-4- scale, weighing the 2009 season most heavily (50%) down to the least-weighted 2005 season (4%) to give better credence to more recent MLB run environments.
This will be the matrix I use in any further research that requires a run expectancy matrix.
Eyeballing the variance between seasons, the data is roughly consistent across the last five years. There didn't appear to be a dramatic trend beyond a subtle, general decrease in expected runs for several events over the last five years. But I preferred to emphasize recent trends over emphasizing the distant past and recent past equally given the always-changing MLB environment.