Most of our billionaires are actually poorer than the millionaires of the 1920s in terms of physical assets. They mostly own imaginary assets such as shares which can up and down in value at any time. Gates is just trying to turn his imaginary fortune into real stuff which will keep a more consistent value over time.

What's actually surprising is that more billionaires aren't doing this. For instance twitter lost $3.5 billion in value over just the last week. The fact is most billionaires can't take more of their money out because people would work out these companies are over valued quite quickly and they'd lose most of their wealth.