Wealth inequality has not increased for three decades when all assets accounted for.

From Social Security and Trends in Wealth Inequality by Sylvain Catherine, Max Miller, and Natasha Sarin.  From the Abstract:

Recent influential work finds large increases in inequality in the U.S. based on measures of wealth concentration that notably exclude the value of social insurance programs. This paper revisits this conclusion by incorporating Social Security retirement benefits into measures of wealth inequality. We find that top wealth shares have not increased in the last three decades when Social Security is properly accounted for. This finding is robust to assumptions about how taxes and benefits may change in response to system financing concerns. When discounted at the risk-free rate, real Social Security wealth increased substantially from $4.8 trillion in 1989 to $41.3 trillion in 2016. When we adjust the discount rate for long-run macroeconomic risk, this increase remains sizable, growing from over $3.9 trillion in 1989 to $33.9 trillion in 2016. Consequently, by 2016, Social Security wealth represents 57% of the wealth of the bottom 90% of the wealth distribution.

For more than a decade, perhaps two, it has been known that a good understanding of the economic conditions of the bottom 20% and even 40% of the income quintiles necessarily requires incorporation of government transfer programs.  Income inequality is much lower when this is done.  It also explains why absolute consumption levels are so much higher for the bottom two quintiles than if you look only at earned income.  

It also creates some interesting insights such as the bottom two income quintiles, all income included, have household incomes and consumption rates near those of the middle class in 1960 or 1970 in real terms.  

This paper is doing the same adjustment on the wealth side of things.  I am not too surprised that there has been not too much increase in wealth inequality over the past three decades.  The top quintile have done exceptionally well from asset valuation increases but Social Security has become increasingly generous, particularly when you take into account other age targeted programs such Medicare.  

Studies such as this are heavily dependent on assumptions and I have not reviewed it in detail but the findings are not a surprise.  Inequality is a desperate rallying cry on the left but it has far less meaning than it did in 1900 or 1950.