Also FYI the computationally expensive part isn't the model, it's the analysis. It turns out that when you have two hundred years of income tax records from dozens of countries you need some pretty powerful hardware. Who would have thought? I mean, not you, since you seemed to have been under the impression that an econometric model isn't talking about a regression model, but rather that computer program from the movie Pi.

fwiw Piketty talks about all of this in theintroductionof the book. I'm surprised you didn't notice it while you were reading the book, since you seem so familiar with the rest of it.