Tom Tango publishes the run expectancy table for 2012-2022. He also provides the probability of scoring, and the percentage of opportunities. I had not realized that over half of plate appearances occur with the bases empty. During the time period above, 56.4% of PA came with the bases empty.

The Day by Day Database has situational batting data back to 1974. During that time, the percentage of PA with the bases empty has been fairly consistent, although 56.4% is at the high end. Of the thirteen seasons at or above 56%, only one happened prior to 2010, the 1988 season. Not surprisingly the percentage was low during the steroid era, as plenty of batters reached base.

Why is the percentage so high now? I believe it has to do with somewhat lower offensive levels combined with a high number of home runs. Home runs clear the bases, and unlike the steroid era, batters aren’t picking up a lot of other hits. So we watch more and more situations with no tension.