Here is what I was able to patch together in my free time.

The countries I’ve filled in were about half of the OECD. The data is hard to get on administrative units elsewhere in the world (I got my data from the OECD website), but it was also hard to get for OECD states. The reason it was hard is because OECD data collectors divide up administrative units into two separate categories (TL2 and TL3) that sometimes correlate to traditional administrative units (such as California or New South Wales) and are sometimes arbitrary creations of EU or OECD bureaucrats designed specifically for data collection (rather than for understanding the historical trajectory of regions within a state).

Does this make sense?

To make matters worse, sometimes the TL2 category correlated with an actual administrative unit with political representation in a capital, and sometimes the TL3 category was the actual administrative…