Wealth concentration is a theoretical[according to whom?] process by which, under certain conditions, newly created wealth concentrates in the possession of already-wealthy individuals or entities. According to this theory, those who already hold wealth have the means to invest in new sources of creating wealth or to otherwise leverage the accumulation of wealth, thus are the beneficiaries of the new wealth. Over time, wealth condensation can significantly contribute to the persistence of inequality within society. Thomas Piketty in his book Capital in the Twenty-First Century argues that the fundamental force for divergence is the usually greater return of capital (r) than economic growth (g), and that larger fortunes generate higher returns [pp. 384 Table 12.2, U.S. university endowment size vs. real annual rate of return]