Arthur: The Royals, the strike zone, and an October surprise

From SABR member Robert Arthur at Baseball Prospectus on October 22, 2014:

Everybody’s been writing about the strike zone recently, and that’s for good reason. The strike zone is evolving, and for the first time in the history of baseball, we have the technology to directly record that evolution. Mostly, the bottom of the strike zone is dropping, and that plays some role in shaping the current pitching-dominated era (although exactly how much of a role is a matter of some debate).

What’s most astonishing about the strike zone’s changing definition is the rapidity with which we are witnessing the results. Year after year, the strike zone falls, and this year has been no exception. In this recent article, Jon Roegele chronicles the most dramatic drop in the bottom of the strike zone yet: In the last year, the zone’s real estate has increased by 16 square inches. But even without a rigorous statistical analysis of the zone, you could feel the impact of the strike zone’s accelerating fall in the numerous strikeout records which have been broken, and in the historic seasons of Clayton Kershaw and other pitchers.

On a whim, I recently looked at how the strike zone varies month to month. I figured that if the change in the zone had been so rapid year to year, maybe there had even been some change during the year.

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Originally published: October 22, 2014. Last Updated: October 22, 2014.