Mark Thoma seems to have provided the first pointer, although others surely will follow.

Summers’ review is the most complete evisceration of Piketty’s economics that has been published to date. But Summers suggests that we sniff the rose, never mind the manure that lies underneath. He writes,

Even in terms of income ratios, the gaps that have opened up between, say, the top .1 percent and the remainder of the top 10 percent are far larger than those that have opened up between the top 10 percent and average income earners. Even if none of Piketty’s theories stands up, the establishment of this fact has transformed political discourse and is a Nobel Prize-worthy contribution.

This is reminiscent of Brad DeLong. It strikes me as intellectual charity driven by ideological sympathy. I encourage everyone reading this blog to do the opposite. Reserve your most charitable interpretations for those whose views disturb you, and adopt the most critical-thinking posture toward those whose views please you.

The bulk of Summers’ review consists of just this sort of critical thinking. Summers writes,

Piketty argues that the economic literature supports his assumption that returns diminish slowly (in technical parlance, that the elasticity of substitution is greater than 1), and so capital’s share rises with capital accumulation. But I think he misreads the literature by conflating gross and net returns to capital. It is plausible that as the capital stock grows, the increment of output produced declines slowly, but there can be no question that depreciation increases proportionally. And it is the return net of depreciation that is relevant for capital accumulation. I know of no study suggesting that measuring output in net terms, the elasticity of substitution is greater than 1, and I know of quite a few suggesting the contrary.

I have not seen this point about the confusion of gross and net return made by anyone else. By DeLong’s standards, that means we should dismiss Summers’ argument. But to my eye, it seems like a powerful criticism. [UPDATE: Oops! A commenter points out that Matt Rognlie had made the exact point about gross and net return.]

Remember the scandal over the Reinhart-Rogoff spreadsheet? This strikes me as considerably worse.

Summers also writes,

Rather than attributing the rising share of profits to the inexorable process of wealth accumulation, most economists would attribute both it and rising inequality to the working out of various forces associated with globalization and technological change.

As in the Smithian theory of inequality.