Let me offer a few immediate reactions.
The book has three main elements:
- A history of inequality and wealth.
- A forecast of how things will evolve over the next century
- Policy recommendations, such as a global tax on wealth.
Point 2 is highly conjectural. Economists are really bad at such things. In particular, the leap from r>g to the conclusion of a growing role of inheritance in society seems too large to me. Many capital owners consume much of the return on their capital, so wealth does not grow at rate r. This consumption ranges from fancy cars and luxurious vacations to generous charitable giving. In addition, unless mating is perfectly assortative, or we return to an era of primogeniture, wealth per family shrinks as it is split among children. So, from my perspective, Piketty tries to draw way too much from r>g. (Quick Quiz for econonerds: (a) What does r>g tell you in a standard overlapping generations model? (b) And what is the magnitude of bequests in that model? Answers below.*)
Point 3 is as much about Piketty’s personal political philosophy as it is about his economics. As we all know, you can’t get “ought” from “is.” Like President Obama and others on the left, Piketty wants to spread the wealth around. Another philosophical viewpoint is that it is the government’s job to enforce rules such as contracts and property rights and promote opportunity rather than to achieve a particular distribution of economic outcomes. No amount of economic history will tell you that John Rawls (and Thomas Piketty) offers a better political philosophy than Robert Nozick (and Milton Friedman).
The bottom line: You can appreciate his economic history without buying into his forecast. And even if you are convinced by his forecast, you don't have to buy into his normative conclusions.
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* Answers to quiz: (a) That the economy is dynamically efficient (that is, it has not over-accumulated capital). (b) Zero.