MLB is considering extra innings to begin with a runner on 2B.
This link gives the chance of scoring under various situations. It also gives expected runs. We can find actual run scoring in each inning here. With a bit of hand-waving we can determine an approximate curve for runs scoring. It looks something this.
normal | on 1B | on 2B | |
Score 0 | 73.00% | 59.00% | 39.00% |
Score Any | 26.60% | 41.00% | 61.00% |
Score 1 | 14.63% | 22.55% | 33.55% |
Score 2 | 6.58% | 10.15% | 15.10% |
Score 3 | 2.96% | 4.57% | 6.79% |
Score 4 | 1.33% | 2.05% | 3.06% |
Score 5+ | 1.09% | 1.68% | 2.50% |
Based on those curves we can determine the odds of teams scoring with a runner at 2nd and no outs, and compare this with the normal rules of baseball, as well as beginning with a runner on 1st.
normal | on 1B | on 2B | |
runs scored | 0.482 | 0.743 | 1.105 |
no score | 53.29% | 34.81% | 15.21% |
1-1 tie | 2.14% | 5.09% | 11.26% |
2-2 tie | 0.43% | 1.03% | 2.28% |
end after inn. | 44.02% | 58.80% | 70.64% |
continues | 55.98% | 41.20% | 29.36% |
Around 55% of extra inning games go on to the next inning with the normal rules. If the inning started with a runner at 2nd, only 29% of games that reach the 10th inning would see an 11th inning.
Inning | normal | on 1B | on 2B |
10 | 8.76% | 8.76% | 8.76% |
11 | 4.90% | 3.61% | 2.57% |
12 | 2.75% | 1.49% | 0.76% |
13 | 1.54% | 0.61% | 0.22% |
14 | 0.86% | 0.25% | 0.07% |
15 | 0.48% | 0.10% | 0.02% |
16 | 0.27% | 0.04% | 0.01% |
17 | 0.15% | 0.02% | 0.00% |
18 | 0.08% | 0.01% | 0.00% |
19 | 0.05% | 0.00% | 0.00% |
20 | 0.03% | 0.00% | 0.00% |
Here's the expected distribution of extra inning games. In the last five years of MLB, 8.76% of games have reached the 10th inning. Just under 5% of games have reached the 11th inning. The numbers here are estimates, but the actual observed games are a pretty close match.