[DocSavage]

The sorted stochastic matrix shows that C contradicts your assumption that it's not possible to switch from a new language to an old one. Or, at least, it shows that portions of new language code are occasionally rewritten in C.

[kem]

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.

[thaumasiotes]

I have defined "new language" in my comment as one so new that no significant projects exist in that language, not as one which is newer than C but still arbitrarily old.

> if you happen to do your measurements after a language has had some uptake but before it's been around for long enough that people have built significant projects on it and subsequently gotten sick of it

By this definition, it is not possible to switch from a new language to anything.

It's stated as a binary, but really this defines a continuum of newness, and the metric of the OP is very sensitive to it.