The wealth of the richest 0.00001% of the U.S. now exceeds that of the prior historical peak, which occurred in the Gilded Age, according to economist Gabriel Zucman. In the late 19th century, the U.S. experienced rapid industrialization and economic growth, creating an inordinate amount of wealth for a handful of families. This era was also known for its severe inequality; and some have called the period that began around 1990 a "Second Gilded Age." Back then, just four families represented the richest 0.00001% today's equivalent is 18 families. Zucman, a French economist whose doctoral advisor was the historical economist Thomas Piketty, author of bestseller "Capital in the Twenty-First Century," released data this week showing that as of July 1, the top 0.00001% richest people in the U.S. held 1.35% of the country's total wealth. These 18 families include those of Jeff Bezos, Mark Zuckerberg and Bill Gates. The richest 0.01% " around 18,000 U.S. families " have also surpassed the wealth levels reached in the Gilded Age. These families hold 10% of the country's wealth today, Zucman wrote. By comparison, in 1913, the top 0.01% held 9% of U.S. wealth, and a mere 2% in the late 1970s. The increasing concentration of wealth comes as the ultra-rich face more scrutiny for the money they're not paying in taxes. Recent reports have highlighted that because so much of their wealth consists of unrealized gains in stocks and real estate, they pay little or nothing in income tax.