A prescient note on the home-market effect by Max Corden


Paul Krugman’s 1980 AER paper formally introduced the home-market effect. In introducing his result, he mentions (p.955):

Notice that this argument is wholly dependent on increasing returns; in a world of diminishing returns strong domestic demand for a good will tend to make it an import rather than an export. But the point does not come through clearly in models where increasing returns take the form of external economies (see W. M. Corden). One of the main contributions of the approach developed in this paper is that by using this approach the home market can be given a simple formal justification.

I doubt that very many people have looked at the Corden reference, as it appeared in a 1970 conference volume titled Studies in international economics. Monash Conference papers. Here’s an excerpt from the surprisingly prescient three-page note:

A note on economies of scale, the size of the domestic market and the pattern of trade

Professor Grubel suggests that a country will tend to produce and export those products or ‘styles’ of products for which it has a relatively large domestic market. He explains this in terms of economies of scale. This is essentially the ‘Linder hypothesis’ which has obtained some empirical support, as well as being intuitively plausible. But it does raise an interesting theoretical question which has not, to my knowledge, been explored. In a simple static two-product two-country model with no transport costs, with economies of scale and with the demand patterns differing between the two countries it does not follow that a country will export that product to which its own demand pattern is biased. In that sort of model, as is well-known, one can say only that at least one of the two countries, and possibly both, will specialise, but one cannot say which country will specialise in which good. From the point of view of maximising potential world income there will be an optimum pattern of specialisation, but this will not depend in any simple predictable way on differences between the demand patterns of the two countries. Thus we cannot obtain the Linder hypothesis from this simple model. The question then is: What else must we put into the model? Is it transport costs, or is it rather something ‘dynamic’ ? In order to focus on the main point I shall now assume that the two countries are of equal size, that their factor endowments and production functions are identical, and that any differences between the factor-intensities of the two products are not large. Hence the two countries have identical convex production transformation curves. They differ only in their demand patterns. Country A’s demand pattern is biased towards product X and country B’s towards product Y. Needless to say, the discussion to follow is very tentative…

A third approach might be to introduce transport costs. Transporting goods from one country to another uses up resources, and from the point of view of maximising world income it will pay to minimise transport costs. Given that in the final equilibrium both countries will specialise, each country should then specialise on the good for which it has the relatively greater demand, since this will minimise transporting. This seems obvious. Provided we do not introduce other complications, trade along Linder lines will maximise potential world income. But it does not seem so easy to prove that trade will actually assume that pattern. Suppose that, for some reason, one starts with the trade flow in the opposite direction. One might explain this in terms of some dynamic considerations. Will there then be a natural tendency for the pattern of specialisation and hence the flow of trade to reverse itself? It does not seem obvious that this would be so. There is scope for further theoretical explorations here.

As Krugman himself has commented: “Now it is always tricky to reread old texts in the light of subsequent information; knowing what actually happened, you can probably find a prophecy of Nostradamus that fits the event, and knowing subsequent developments in economic theory, you can probably find most of it hinted at in Ibn Khaldun.” Still, I think Corden was onto something in 1970.