"Academic Age" of Authors of American Economic Review Articles

Torgler and Piatti have written a massive paper on the American Economic Review with heaps of tables, graphs, and regression analyses. This is what most caught my eye:Academic age is the number of years since an author got their PhD. The modal author of an AER article is about 4 years post PhD and there's quite a low probability of publication more than 20 years post-PhD. Maybe this is why people