The New York Times on Exchange Rates

Greg Mankiw and Dean Baker are beating up on an editorial in today’s New York Times. I think their attacks are a bit unfair. The editorial says that the Bush administration is reducing the trade deficit by “letting the dollar slide,” which the Times suggests is not a good idea, but instead, “to be truly effective, a weaker dollar must be paired with higher domestic savings.” Greg and Dean ridicule the editorial by pointing out that a weaker dollar is exactly the mechanism by which higher domestic savings would reduce the trade deficit. (Dean also allows for the possibility that higher savings could cause a recession, which would reduce the trade deficit but obviously would not be desirable.) So if “letting the dollar slide” is a bad thing, they suggest, how could increasing domestic savings be a good thing, when increasing domestic savings would only cause the dollar to slide further?

I grant you the editorial does not appear to have been written by someone who had just finished getting an A in a course in open economy macroeconomics, but I think the editorial has a point, which Greg and Dean are missing. There are two reasons that the dollar can weaken. First, it can weaken because US interest rates fall (relative to foreign rates), making dollars less attractive. That is a “movement along” the demand curve for dollars. Second, it can weaken because people demand fewer dollars at any given interest rate. That is a “shift” in the demand curve for dollars*. What the Times is saying is that the right way to weaken the dollar is by inducing a movement along the demand curve, whereas Bush administration policies are instead causing the curve to shift.

While it’s debatable just how much influence public policy has on the position of the demand curve, it certainly has some influence. Surely Dean Baker, who perpetually complains about the Clinton-Rubin strong dollar policy, will not deny this. I’m personally skeptical about Dean’s maintained hypothesis that Clinton-Rubin policies had much impact on dollar demand, but I think there is a good case to be made that the Bush policies identified by the Times do have considerable impact. When a nation continues to run budget deficits in the face of a negative personal savings rate, there is a tendency for investors to lose confidence in that nation’s currency and to demand less of it at any given interest rate.

The difference in effect between a shift in the demand curve and a movement along the curve is important, though I don’t think the Times identifies that difference quite correctly, or at least the Times doesn’t make the true difference clear. The editorial implies that a shift in the currency demand curve is more inflationary than a movement along that curve. That may be true in the long run, but it's not obvious that it’s true in the short run. The true difference (assuming monetary policy is working well) is that, with a shift in the demand curve, the stimulus from the improved trade balance is offset by reduced domestic investment, whereas, with a movement along the curve (assuming that movement results from increased domestic savings), the stimulus is offset by reduced consumption. I think Greg and Dean will agree that the latter is preferable.

In the long run, less investment leads to a lower growth rate of productive capacity, which slows the rate of labor productivity growth, and much contemporary opinion holds that slowing productivity growth brings about an unfavorable shift in the Phillips curve, causing inflation to accelerate more rapidly (or decelerate less rapidly) at any given level of employment. Thus, in a sense the Times is right to argue that the “shift” strategy is inflationary (because it reduces investment). Perhaps the anticipation of such future inflationary conditions is what reduces the Fed’s “room to maneuver” in the face of a weakening currency. The Times doesn’t spell out this argument, but it makes some sense to me if that’s what they had in mind.


* In the model I have in mind, the quantity of dollars demanded depends on relative interest rates, and then the foreign exchange value of the dollar depends on the quantity demanded (as if the supply of dollars in the foreign exchange market were perfectly inelastic). The demand curve to which I refer represents the first relationship, and the value of the dollar is then determined by the second relationship. Obviously this is a simplification, since the bond markets and the foreign exchange market have to come into equilibrium simultaneously, and there really is not a perfectly inelastic supply of dollars. For purposes of the present analysis, however, I don’t think this simplification distorts the point I’m trying to make.