That's almost a tautology then. If you only know one thing about someone, that's also necessarily the best predictor for anything about them. However, it doesn't tell us much about whether wealth does concentrate over time.
> Really.... ? Why?
Because regimes change all the time despite rulers being alive. The death of a ruler by old age rarely triggers regime change, they just get succeeded by someone else. It's usually another event that triggers regime change (peaceful and violent revolutions, war, etc.). Immortal rulers wouldn't be immune to those events.