Michael Barone‘s latest column makes clear that he’s not particularly convinced by the arguments Thomas Piketty has used to woo American leftists.

There is general agreement that Piketty has compiled an impressive array of data on income inequality in multiple nations going back 200 years or more. There is agreement also that he thoughtfully states caveats and cautions about data interpretation. His thesis seems at least plausible at a time when the very top incomes have increased much more rapidly than those at the middle and bottom. Even some critics acknowledge that, as the Washington Post’s Robert Samuelson writes: “the present concentration of income and wealth feels excessive. It understandably stirs resentment.”

But is his picture of current trends complete? The Manhattan Institute’s Scott Winship points out that relying, as Piketty does, on tax returns for the U.S. statistics means omitting income from Social Security, food stamps, public housing, Medicare, and Medicaid. Tax returns count roommates and unmarried partners as separate units when they are part of a larger household. They don’t include employer-paid health insurance — an increasing share of employee compensation in recent decades. Including these factors, Winship notes, means that incomes below the top 10 percent have not stagnated but have risen significantly since the 1970s. Increasing inequality is compatible with increases in ordinary people’s incomes.

Economist Tyler Cowen takes issue with another of Piketty’s assumptions, that the rich can earn 4 to 5 percent on their wealth “automatically, with the mere passage of time, rather than as the result of strategic risk-taking.” The French economist, Cowen says, has “a notion of capital as a growing, homogeneous blob” when in fact “sudden reversals and retrenchments are inevitable.” …

… “There’s a persistent tension,” writes Bloomberg’s Clive Crook, “between the limits of the data [Piketty] presents and the grandiosity of the conclusions he draws.” Like global-warming alarmists, he extrapolates from abstract theory and a few years’ trendlines out a century forward — and presents the results as inevitable. He also presents them as justifying the confiscation, more or less, of wealth accumulated by private individuals and putting it in the hands of mandarins guided by their supposedly superior sensitivity to public welfare. There might be less inequality in such a world, but also less economic growth and a lower, though more equal, standard of living.

“In perhaps the most revealing line of the book,” Cowen writes, “the 42-year-old Piketty writes that since the age of 25, he has not left Paris, ‘except for brief trips.’” France, where a cozy elite runs government and large corporations, has a 75 percent top-income-tax rate and essentially zero economic growth. Is that the future American liberals want?