It's absolutely a rebuttal. If you're making a statistical/empirical claim, especially one that goes against orthodox economic theory, than robustness to the un

It's absolutely a rebuttal. If you're making a statistical/empirical claim, especially one that goes against orthodox economic theory, than robustness to the underlying assumptions is really important. Subsequently empirical research has found that Piketty's conclusions are extremely sensitive to the way he slices the historical data and the modeling parameters. At best that's evidence of an incompetent econometrician who doesn't understand the tools enough to perform the required robustness checks. At worse, it's evidence of data snooping to shoehorn the the results into a pre-determined hypothesis. But you don't have to take my word for it. The IMF itself performed an exhaustive robustness check and found that Piketty's conclusions simply don't hold up: https://www.imf.org/external/pubs/ft/wp/2016/wp16160.pdf https://www.imf.org/external/pubs/ft/wp/2016/wp16160.pdf