The distribution of wealth throughout the population is often closely approximated by a Pareto distribution, with tails which decay as a power-law in wealth. (See also: Distribution of wealth and Economic inequality). According to PolitiFact and others, the 400 wealthiest Americans had "more wealth than half of all Americans combined."[1][2][3][4] Inherited wealth may help explain why many Americans who have become rich may have had a "substantial head start".[5][6] In September 2012, according to the Institute for Policy Studies, "over 60 percent" of the Forbes richest 400 Americans "grew up in substantial privilege".[7]