The stat I checked out a couple of years ago suggested that it was around 24% of games decided by 1 run, simple to round up to one quarter.
Certain higher-scoring parks will obviously allow for more run-line action (assuming the question relates to that) and there are several sites that have stats for W-L on 1-run games, which you can easily convert into a run-line stat, for prior years. Probably there's sites out there with run-line stats but a few I use, and trust, can be easily converted, as mentioned.
I've got no issue with appropriate run-line plays despite the harping I've heard in the past.
Stats can lie but politicians can also tell the truth.
From time to ...
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