A new book-length study on the tax burden of the ultrarich begins with a startling finding: In 2018, for the first time in history, America's richest billionaires paid a lower effective tax rate than the working class. The Triumph of Injustice," by economists Emmanuel Saez and Gabriel Zucman of the University of California at Berkeley, presents a first-of-its kind analysis of Americans' effective tax rates since the 1960s. It finds that in 2018, the average effective tax rate paid by the richest 400 families in the country was 23 percent, a full percentage point lower than the 24.2 percent rate paid by the bottom half of American households. In 1980, by contrast, the 400 richest had an effective tax rate of 47 percent. In 1960, that rate was as high as 56 percent. The effective tax rate paid by the bottom 50 percent, by contrast, has changed little over time. The tipping point came in 2017, with the passage of the Tax Cuts and Jobs Act. The legislation, championed by President Trump and then-House Speaker Paul D. Ryan (R-Wis.), was a windfall for the wealthy: It lowered the top income tax bracket and slashed the corporate tax rate. By 2018, according to Saez and Zucman, the rich were already enjoying the fruits of that legislation: The average effective tax rate paid by the top 0.1 percent of households dropped by 2.5 percentage points. The benefits promised by the bill's supporters - higher rates of growth and business investment and a shrinking deficit - have largely failed to materialize.