This dataset certainly does not do this adequately. This is a very active area of research, and it will take a long time before we converge to reasonable estima

This dataset certainly does not do this adequately. This is a very active area of research, and it will take a long time before we converge to reasonable estimates of the past. Even today, countries routinely change their GDP figures after a few years because of how difficult such a thing is to to measure. You should mentally put large error bars on these graphs. The fact that they don't come up with them already is concerning.