Pg's main point is that the major source of wealth inequality comes from wealth creators as opposed to wealth exploiters. The wealth creators are typical startups and people creating new industries while wealth exploiters are the one playing high frequency trading, lobbing congress, buying up real estate, creating monopolies, investing with insider info and so on. My gut feeling is that wealth creation part is in reality less than 20%. This intuition is based on simple fact that wealthy people have managed to far more disproportionately increase their wealth than what comes from increase in GDP or other measures of productivity. There is plenty of analysis available in Capital book that clearly suggests that wealthy people mainly invests in non-productive investment instruments such as real estate that has nothing to do with increasing productivity of the society. It just constraints the supply side, inflating prices and thus increasing value of the investment. These investment tools enables them to transform themselves to become passive wealth exploiters with a setup that generates massive multi-generational income and wealth increase without proportional need for positive contribution to society. There was a very well written article with data analysis on HN that proved that most increase in wealth for top 1% came from these non-productive investment tools such as real estate. This is like wealthy people grouping up to buy loads of the fresh water and inflating prices so average people now must pay majority of income in buying water. So wealth transfer from common people to rich occurs through inflated water prices. Of course, if wealthy people really did this for water, they will be in trouble and revolutions will break out. However doing this for real state raises no eye brows even though real estate is essential need for humans.
A fun fact: Despite of giving billions and without starting any new blockbuster companies, Bill Gates has managed to increase his wealth by more than 50% since he officially retired. He has sure helped few startups but it would be too funny as well as cruel to think that most of his wealth gain comes via helping startups or causing productivity gains in society. Last I checked his billions are managed by hedge fund like setup who typically have goal to maximize returns through non-productive instruments such as real estate, HFT, commodity market games, derivatives etc and they rarely devote more than 20% of portfolio to truely productive activities such as startups.
It is also marvelous how some of the wealthiest have outright bought the laws for themselves, for example, middle class in US universally pays almost twice the tax rates than top 1%. This would be unthinkable in previous generation. The entire capital tax gimmic is put in to law with a full knowledge that it does not benefit majority of citizens who have little or no savings, let alone investments for short term trading. It is purely designed to benefit top 1% who derives large chunk of income as capital gains. The most depressing thing is that the field is becoming less and less level playing, for example wealthy can buy out admissions in best universities while average citizens are getting priced out from same institutions. The significant increase in mortgage and student debt load combined with long term stagnant wages now eliminates possibility of savings or investments and therefore risk taking. I suppose this wasn't exactly like this in 70s when many more people had decent savings, had ability for some risk taking and lot of them even actually were able to retire. In our generation most people don't even think of retirement anymore except in tech industry which is probably less than 5% of population. We in tech field are perhaps not so much impacted and so world looks little different from our glasses, especially if you had been college dropout or without family. However for a common citizen with a family, mortgage, healthcare bills, no savings, retirement funds uncertainty and student loans it is much more difficult to cross the chasm than it used to be in 70s.