Piketty and his critics

Nate Silver explains why we should be skeptical of both Piketty and his skeptics.

Piketty’s data sets are very detailed, and they aggregate data from many original sources. For instance, the data Piketty and the economist Gabriel Zucman compiled on wealth inequality in the United Kingdom for their paper “Capital is Back: Wealth-Income Ratios in Rich Countries, 1700-2010″ contains about 220 data series for the U.K. alone which are hard-coded into their spreadsheet. These data series are compiled from a wide array of original sources, which are reasonably well documented in the spreadsheet.

This type of data-collection exercise — many different data series over many different years, compiled from many countries and many sources — offers many opportunities for error. Part of the reason Piketty’s efforts are potentially valuable is because data on wealth inequality is lacking. But that also means his numbers will not have received as much scrutiny as other data sets.


What error rate is acceptable? The right answer is probably not “zero.” If researchers kept scrubbing data until it were perfect, they’d never have time for analysis. There comes a point of diminishing returns; that Hack Wilson had 191 RBIs during the 1930 season rather than 190 ought not have a material impact on any analysis of baseball player performance. At other times, entire articles or analyses or theories or paradigms are developed on the basis of deeply flawed data.

I don’t know where Piketty sits on this spectrum. However, I think Giles (and some of the commentary surrounding his work) could do a better job of describing Piketty’s error rate relative to the overall volume of data that was examined. If Giles scrutinized all of Piketty’s data and found a handful of errors, that would be very different from taking a small subsample of that data and finding it rife with mistakes.

It's striking how much discussion of Piketty's book has happened already. As Silver notes, this is peer review happening live and in the open.

That makes the book itself, which sits in my Kindle, already somewhat dated. I'd love for the Kindle or some other ebook service to evolve to be a platform for living books. You could see the original text, but the book itself would accumulate references and edits and notes from both the author and readers.

When I think of books as a social platform, I don't think of Goodreads, I think of living texts. That would be truly exciting, and the first book platform to support that would achieve some serious network effects. It's odd that in the age of the ever-living web page that our e-books are still so static and rigid in form. I'm still not sure why I can't leave notes on passages in books for friends and followers to discover when they open the text in their e-reader.