A research report from business school professors at Imperial College, Columbia and U of Maryland found that wealthy investors get returns on bonds and stocks that are "up to 70 per cent times greater returns on their investments than those with modest wealth." This is a point that Piketty makes strongly, backing it up by analyzing data from the Harvard endowment, which gets 10% returns on its ~$80B nest-egg, while the rest of us barely clear inflation with our savings.