What's missing from the matrix is "no language" language or null language. That is, a column and row that represents people who start projects from scratch in a given language.
I agree that the analysis makes it abundantly clear people move to older languages, but the question is what new projects are started in, and how many projects represent new versus transitioned projects.
This analysis is interesting, and gives a rough idea of what people are moving from and to when they decide to do that, but not necessarily popularity.
What the author is indexing in the end isn't really predicted overall language use, it's predicted transition target frequency.
I agree that the analysis makes it abundantly clear people move to older languages, but the question is what new projects are started in, and how many projects represent new versus transitioned projects.
This analysis is interesting, and gives a rough idea of what people are moving from and to when they decide to do that, but not necessarily popularity.
What the author is indexing in the end isn't really predicted overall language use, it's predicted transition target frequency.