Those are the symbols for the “real exchange rate,” or the terms of trade, both measured inversely, or “competitiveness,” measured directly. That is, when this expression goes up, the real exchange rate depreciates, the terms of trade worsen, and competitiveness improves. e is the nominal exchange rate. Say that we are Japan, and e is yen/dollar. As e goes up, it means that our exchange rate is depreciating. (I am forever confused by that way of writing e, but that’s how it’s done.) P* is the domestic price index of our trading partners, and P is our domestic price index. Suppose that we (Japan) are relatively deflationary, which means that P*/P is going up. That has the same effect as a currency depreciation.

It appears to me that Japan is experiencing both a nominal currency depreciation (a rise in e) and an increase P*/P. That means that Japan is certainly experiencing a real exchange rate depreciation, or a real deterioration in its terms of trade. It has to give up more Toyotas to import the same amount of beef. In terms of purchasing power in world markets, the Japanese are becoming worse off.

At the same time, Japan has become more competitive. Japanese consumers will be inclined to import less beef. Toyota will find itself able to export more cars.

The question I have is this: when does Japan succeed in inflating away some of its debt? In terms of world purchasing power, it is already doing so. Japanese holders of government bonds are earning negative returns relative to the cost of a consumption basket. But that does not help the government. The government needs an increase in yen-denominated tax revenue.

Possibly related: Brad DeLong writes,

That process–the rise in domestic nominal prices and wages, and the larger fall in the nominal value of the currency–may derange the price system and so disrupt aggregate supply. The new equilibrium may be one in which the real depreciation of the currency is expansionary in the sense that it tends to push real aggregate demand above potential output. But the economy may nevertheless be in depression, if the process of getting to the new equilibrium has entailed nominal price swings large enough to have been sufficiently disruptive to the market-mediated division of labor. Weimar 1923.

Pointer from Mark Thoma.

I see that as the crux of the issue. If investors lose confidence in Japan’s bonds, the Japanese government loses its ability to borrow. When you lose the ability to borrow and you are running large deficits, watch out.

UPDATE: Read Tyler Cowen’s post on this topic.