In an NBER working paper, David Weil argues that Thomas Piketty overestimates wealth inequality. In the abstract of the paper, Weil writes:
In Capital in the 21st Century, Thomas Piketty uses the market value of tradeable assets to measure both productive capital and wealth. As a measure of wealth this is problematic because it ignores the value of human capital and transfer wealth, which have grown enormously over the last 300 years. Thus the constancy of the wealth/income ratio as portrayed in his data is an illusion. Further, the types of wealth that he does not measure are more equally distributed than tradeable assets. The approach also incorrectly identifies capital gains due to reduced discount rates as increases in the capital stock.