On global safe assets
If you look at the world today, it's very much still dollar-centric ... The U.S. is really sort of the world banker. As such, it enjoys an exorbitant privilege and it also bears exorbitant duties. Directly or indirectly, it's the pre-eminent supplier of safe and liquid assets to the rest of the world. It's the issuer of the dominant currency of trade invoicing. And it's also the strongest force in global monetary policy as well as the main lender of last resort.
If you think about it, these attributes reinforce each other. The dollar's dominance in trade invoicing makes it more attractive to borrow in dollars, which in turn makes it more desirable to price in dollars. And the U.S. role as a lender of last resort makes it safer to borrow in dollars. That, in turn, increases the responsibility of the U.S. in times of crisis. All these factors consolidate the special position of the U.S.
But I don't think that it's a very sustainable situation. More and more, this hegemonic or central position is becoming too much for the U.S. to bear.
The global safe asset shortage is a manifestation of this limitation. In my view, there's a growing and seemingly insatiable global demand for safe assets. And there is a limited ability to supply them. In fact, the U.S. is the main supplier of safe assets to the rest of the world. As the size of the U.S. economy keeps shrinking as a share of the world economy, so does its ability to keep up with the growing global demand for safe assets. The result is a growing global safe asset shortage. It is responsible for the very low levels of interest rates that we see throughout the globe. And it is a structural destabilizing force for the world economy. ...
In my view, the global safe asset shortage echoes the dollar shortage of the late 1960s and early 1970s. At that time, the U.S. was the pre-eminent supplier of reserve assets. The global demand for reserve assets was growing because the rest of the world was growing. And that created a tension, which was diagnosed by Robert Triffin in the early '60s: Either the U.S. would not satisfy this growing global demand for reserve assets, and this lack of liquidity would create global recessionary forces, or the U.S. would accommodate this growing global demand for reserve assets, but then it would have to stretch its capacity and expose itself to the possibility of a confidence crisis and of a run on the dollar. In fact, that is precisely what happened. Eventually, exactly like Triffin had predicted, there was a run on the dollar. It brought down the Bretton Woods system: The dollar was floated and that was the end of the dollar exchange standard.
Today, there is a new Triffin dilemma: Either the U.S. does not accommodate the growing global demand for safe assets, and this worsens the global safe asset shortage and its destabilizing consequences, or the U.S. accommodates the growing global demand for safe assets, but then it has to stretch itself fiscally and financially and thereby expose itself to the possibility of a confidence crisis. ...For a readable overview of Farhi's views on global safe assets, a useful start is "The Safe Assets Shortage Conundrum," which he wrote with Ricardo J. Caballero and Pierre-Olivier Gourinchas, in the Summer 2017 issue of the Journal of Economic Perspectives (31:3, pp. 29-46. )
Basically, I think that the role of the hegemon is becoming too heavy for the U.S. to bear. And it's only a matter of time before powers like China and the eurozone start challenging the global status of the dollar as the world's pre-eminent reserve and invoicing currency. It hasn't happened yet. But you have to take the long view here and think about the next decades, not the next five years. I think that it will happen.
On some implications for public finance if many economic agents aren't fully rational and don't pay full attention to taxes
There is a basic tenet of public taxation called the dollar-for-dollar principle of Pigouvian taxation. It says that if the consumption of a particular good generates a dollar of negative externality, you should impose a dollar of tax to correct for this externality. For example, if consuming one ton of carbon generates a certain number of dollars of externalities, you should tax it by that many dollars.
But that relies on the assumption that firms and households correctly perceive this tax. If they don't — maybe they aren't paying attention — then you have to relax this principle. For example, if I pay 50 percent attention to the tax, the tax needs to be twice as big. That's a basic tenet of public finance that is modified when you take into account that agents are not rational.
In public finance, there is also a traditional presumption that well-calibrated Pigouvian taxes are better than direct quantity restriction or regulations because they allow people to express the intensity of their preferences. Recognizing that agents are behavioral can lead you to overturn this prescription. It makes it hard to calibrate Pigouvian taxes, and it also makes them less efficient. Cruder and simpler remedies, such as regulations on gas mileage, are more robust and become more attractive.Aggregate production functions, the disaggregation problem, and the Cambridge-Cambridge controversy
There's an interesting episode in the history of economic thought. It's called the Cambridge-Cambridge controversy. It pitted Cambridge, Massachusetts — Solow, Samuelson, people like that — against Cambridge, U.K. — Robinson, Sraffa, Pasinetti. The big debate was the use of an aggregate production function.
Bob Solow had just written his important article on the Solow growth model. That's the basic paradigm in economic growth. To represent the possibility frontiers of an economy, he used an aggregate production function. What the Cambridge, U.K., side attacked about this was the idea of one capital stock, one number. They argued that capital was very heterogeneous. You have buildings, you have machines. You're aggregating them up with prices into one capital stock. That's dodgy.
It degenerated into a highly theoretical debate about whether or not it's legitimate to use an aggregate production function and to use the notion of an aggregate capital stock. And the Cambridge, U.K., side won. They showed that it was very problematic to use aggregate production functions. Samuelson conceded that in a beautiful paper constructing a disaggregated model that you could not represent with an aggregate production function and one capital stock.
But it was too exotic and too complicated. It went nowhere. The profession moved on. Today, aggregate production functions are pervasive. They are used everywhere and without much questioning. One of the things David [Baqaee] and I are trying to do is to pick up where the Cambridge-Cambridge controversy left. You really need to start with a completely disaggregated economy and aggregate it up. ...
We have a name for our vision. We call it "macro as explicitly aggregated micro." The idea is you need to start from the very heterogeneous microeconomic environment to do justice to the heterogeneity that you see in the world and aggregate it up to understand macroeconomic phenomena. You can't start from macroeconomic aggregates. You really want to understand the behavior of economic aggregates from the ground up.
For example, you can't just come up with your measure of aggregate TFP [total factor productivity] and study that. You need to derive it from first principles. You need to understand exactly what aggregate TFP is. I talked about aggregate TFP and markups, but the agenda is much broader than that. It bears on the elasticity of substitution between factors: between capital and labor, or between skilled labor, unskilled labor, and capital. It bears on the macroeconomic bias of increasing automation. It bears on the degree of macroeconomic returns to scale underlying endogenous growth. It bears on the gains from trade and the impact of tariffs. In short, it is relevant to the most fundamental concepts in macroeconomics.
For a retrospective recounting of what happened in the Cambridge-Cambridge controversies, a useful starting point is Avi J. Cohen and G. C. Harcourt. 2003. "Retrospectives: Whatever Happened to the Cambridge Capital Theory Controversies?" Journal of Economic Perspectives, 17 (1): 199-214.