Para quem queria uma avaliação mais "teorético-formal" do modelo econômica subjacente às ideias do Piketty em seu livro "Capital in the 21st century", veja nesse link aqui a excelente crítica de Per Krusell (Stockolm University) e Tony Smith (Yale University). Trechos abaixo:
Thomas Piketty’s recent book Capital in the Twenty-First Century is a timely and important contribution that turns our attention to striking long-run trends in economic inequality. A large part of the book is thus a documentation of historical data, going further back in time, and focusing more on the very richest in society, than have most existing economic studies. This work is bound to remain influential. A central theme in the book, however, goes beyond mere documentation: as the title of the book suggests, it makes predictions about the future. Here, Piketty argues forcefully that future declines in economic growth -- stemming from slowdowns in technology or drops in population growth—will likely lead to dramatic concentrations of economic and political power through the accumulation of capital (or wealth) by the very richest. These predictions are the subject of the present note.
We emphasize, first, that Piketty’s predictions are not mere extrapolations from past data but, instead, rest importantly on the use of economic theory. This is important, since for the predictions to be reliable, one would want to feel some comfort in the particular theory that is used. Our main point is to make clear that there are strong reasons to doubt the specific theory that Piketty advances.
We argue that one of the key building blocks in this theory—what he calls the second fundamental law of capitalism—is rather implausible, for two reasons. First, we demonstrate that it implies saving behavior that, as the growth rate approaches zero, requires the aggregate economy to save 100% of GDP each year. Such behavior is clearly hard to square with any standard theories of how individuals save, and it is inconsistent with the findings in the empirical literature on how individuals actually save.
Second, we look at aggregate U.S. data to try to compare Piketty’s assumption to standard, alternative theories, and we find that the data speaks rather clearly against Piketty’s theory. Equipped with theories that we find more plausible, we show that even if the rate of economic growth were to decline all the way to zero, inequality would increase only ratio, the centerpiece of Piketty’s analysis of capitalism, does not explode but rather increases only modestly. In conclusion, at least from the perspective of the theory that we are more used to and find more a priori plausible, the second law of capitalism turns out to be neither alarming nor worrisome, and Piketty’s argument that the capital-to-income ratio is poised to skyrocket does not seem well-founded.Ao fim eles afirmam:
Using these models as a basis for prediction, we robustly find very modest effects of a declining growth rate on the capital-output ratio, and hence on inequality. Thus, we find Piketty’s second law quite misleading, and certainly not fundamental; we in fact think that the fundamental causes of wealth inequality are to be found elsewhere.