Folks those are the charts he shares because those were the numbers he had. From what I understand he didn’t have 2020 or beyond and I think he didn’t have before 2013 (though I’m a little iffier on that one)
We had fun discussing these slides on episode 268 of Mastering Dungeons. The data there is surprising, but also it's a very specific set of years that mean very specific things in the history of D&D. This makes the data both very circumstantial and also still interesting to ponder for the future.