I wonder what factors caused that change. Wars and emigration maybe have something to do with it?
I wonder what factors caused that change. Wars and emigration maybe have something to do with it?
Data like these are interesting, but you still need the deep historical context to make sense of what it all means. Of course, for the overall big picture, you couldn't do better than Thomas Piketty's _Capital in the Twenty-First Century_.
There may also be a "hidden wealth" effect as people move it offshore; is someone domiciled in the Cayman Islands who lives in the UK for <6mo a year part of the "UK" graph?
In 1900 there were almost no taxes - A lot of taxation is not just for 'services' - it's distributional. So there's that.
Literacy, voting, emancipation - this to me is the biggest in the long run. People have skills, professions, they can create/read contracts, everyone can hire a lawyer, there is rule of law. There's much dynamism and much ado. In 1900 almost all of us lived on farms. The economy is way more diversified now.
Labour Unions - just started real power about then. Also maybe an awakening in business: Ford paid his staff a lot more so they could actually buy Model T's. There's some deep insight there.
Mass Media - radio, TV, internet. Information equalizers.
Gender Equality - female workforce participation exploded during the war and I think peaked about 20 years ago. This is a massive shift in economic outcomes.
Teddy Roosevelt - he broke up 40 (!!!) monopolies. Wow. Think about that. Basically, America was possibly taken over by corporate cabals who, in a less diversified economy could control everything. This was I think a huge thing. And though we can think of G, FB etc as monopolies, I don't think they have quite the relative strength. I'm still more worried about Wallmart and Amazon ...
The OP's section on "methodology" touches on "lack of transparency".