Daniel J. Mitchell

Why do statists make so many mistakes with data? Paul Krugman, for instance, has butchered numbers when writing about fiscal policy in nations such asFrance, Estonia, Germany, and the United Kingdom.

But Krugman isn’t alone. We also have Thomas Piketty, who was lionized by the left after publication of Capital in the Twenty-First Century.

Ever since his book was published, various experts have called into question the veracity of Piketty’s numbers. Most recently, here’s some of what Alan Reynolds, my colleague at the Cato Institute, wrote about his data for the Wall Street Journal.

Thomas Piketty…remains a hero on the left, but the honeymoon may be drawing to a sour close as evidence mounts that his numbers don’t add up. …data are so misleading as to be worthless. They attempt to estimate top U.S. wealth shares on the basis of that portion of capital income reported on individual income tax returns—interest, dividends, rent and capital gains. This won’t work because federal tax laws in 1981, 1986, 1997 and 2003 momentously changed (1) the rules about which sorts of capital income have to be reported, (2) the tax incentives to report business income on individual rather than corporate tax forms, and (3) the tax incentives for high-income taxpayers to respond to lower tax rates on capital gains and dividends by realizing more capital gains and holding more dividend-paying stocks.

Daniel J. Mitchell

Daniel J. Mitchell is a top expert on tax reform and supply-side tax policy at the Cato Institute.

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