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1、A Theory of Optimum Currency Areas1 Robert A. MundellIt is patently obvious that periodic balance-of-payments crises will remain an integral feature of the international economic system as long as fixed exchange rates and rigid wage and price levels prevent the international price system from fulfil
2、ling a natural role in the adjustment process. It is, however, far easier to pose the problem and to criticize the alternatives than it is to offer constructive and feasible suggestions for the elimination of what has become an international disequilibrium system.2 This chapter, unfortunately, illus
3、trates that proposition by cautioning against the practicability, in certain cases, of the most plausible alternative: a system of national currencies connected by flexible exchange rates. A system of flexible exchange rates is usually presented, by its proponents,3 as a device whereby depreciation
4、can take the place of unemployment when the external balance is in deficit, and appreciation can replace inflation when it is in surplus. But the question then arises whether all existing national currencies should be flexible. Should the Ghanian pound be freed to fluctuate against all currencies or
5、 ought the present sterling-area currencies remain pegged to the pound sterling? Or, supposing that the Common Market countries proceed with their plans for economic union, should these countries allow each national currency to fluctuate, or would a single currency area be preferable? The problem ca
6、n be posed in a general and more revealing way by defining a currency area as a domain within which exchange rates are fixed and asking: What is the appropriate domain of a currency area? It might seem at first that the question is purely academic, since it hardly appears within the realm of politic
7、al feasibility that national currencies would ever be abandoned in favor of any other arrangement. To this, three answers can be given: (1) Certain parts of the world are undergoing processes of economic integration and disintegration, new experiments are being made, and a conception of what constit
8、utes an optimum currency area can clarify the meaning of these experiments; (2) those countries, like Canada, that have experimented with flexible exchange rates are likely to face particular problems which the theory of optimum currency areas can elucidate if the national currency area does not coi
9、ncide with the optimum currency area; and (3) the idea can be used to illustrate certain functions of currencies that have been inadequately treated in the economic literature and that are sometimes neglected in the consideration of problems of economic policy. Currency Areas and Common Currencies A
10、 single currency implies a single central bank (with note-issuing powers) and therefore a potentially elastic supply of interregional means of payments. But in a currency area comprising more than one currency, the supply of international means of payment is conditional upon the cooperation of many
11、central banks; no central bank can expand its own liabilities much faster than other central banks without losing reserves and impairing convertibility.4 This means that there will be a major difference between adjustment within a currency area that has a single currency and a currency area involvin
12、g more than one currency; in other words, there will be a difference between interregional adjustment and international adjustment even though exchange rates in the latter case are fixed. To illustrate this difference, consider a simple model of two entities (regions or countries), initially in full
13、 employment and balance-of-payments equilibrium, and see what happens when this equilibrium is disturbed by a shift of demand from the goods of entity B to the goods of entity A. Assume that money wages and prices cannot be reduced in the short run without causing unemployment, and that monetary aut
14、horities act to prevent inflation. Suppose first that the entities are countries with national currencies. The shift of demand from B to A causes unemployment in B and inflationary pressure in A.5 To the extent that prices are allowed to rise in A, the change in the terms of trade will relieve B of
15、some of the burden of adjustment. But, if A tightens credit restrictions to prevent prices from rising, all the burden of adjustment is thrust onto country B; what is needed is a reduction in Bs real income, and if this cannot be effected by a change in the terms of trade- because B cannot lower, an
16、d A will not raise, prices-it must be accomplished by a decline in Bs output and employment. The policy of surplus countries in restraining prices therefore imparts a recessive tendency to the world economy on fixed exchange rates or (more generally) to a currency area with many separate currencies.
17、6 Contrast this situation with that where the entities are regions within a closed economy lubricated by a common currency, and suppose now that the national government pursues a full-employment policy. The shift of demand from B to A causes unemployment in region B and inflationary pressure in regi
18、on A and a surplus in As balance of payments.7 To correct the unemployment in B the monetary authorities increase the money supply. The monetary expansion, however, aggravates inflationary pressure in region A: indeed, the principal way in which the monetary policy is effective in correcting full em
19、ployment in the deficit region is by raising prices in the surplus region, turning the terms of trade against B. Full employment thus imparts an inflationary bias to the multiregional economy or (more generally) to a currency area with a common currency. In a currency area comprising different count
20、ries with national currencies, the pace of employment in deficit countries is set by the willingness of surplus countries to inflate. But in a currency area comprising many regions and a single currency, the pace of inflation is set by the willingness of central authorities to allow unemployment in
21、deficit regions. The two systems could be brought closer together by an institutional change: Unemployment could be avoided in the world economy if central banks agreed that the burden of international adjustment should fall on surplus countries, which would then inflate until unemployment in defici
22、t countries is eliminated; or a world central bank could be established with power to create an international means of payment. But a currency area of either type cannot prevent both unemployment and inflation among its members. The fault lies not with the type of currency area but with the domain o
23、f the currency area. The optimum currency area is not the world. Optimality is here defined in terms of the ability to stabilize national employment and price levels. National Currencies and Flexible Exchange Rates The existence of more than one currency area in the world implies (by definition) var
24、iable exchange rates. In the international trade example, if demand shifts from the products of country B to the products of country A, a depreciation by country B or an appreciation by country A would correct the external imbalance and also relieve unemployment in country B and restrain inflation i
25、n country A. This is the most favorable case for flexible rates based on national currencies. Other examples, however, might be equally relevant. Suppose that the world consists of two countries, Canada and the United States, each of which has separate currencies. Also assume that the continent is d
26、ivided into two regions that do not correspond to national boundaries-the East, which produces goods such as cars, and the West, which produces goods such as lumber products. To test the flexible-exchange-rate argument in this example assume that the U.S. dollar fluctuates relative to the Canadian d
27、ollar, and that an increase in productivity (say) in the automobile industry causes an excess demand for lumber products and an excess supply of cars. The immediate impact of the shift in demand is to cause unemployment in the East and inflationary pressure in the West, and a flow of bank reserves f
28、rom the East to the West because of the formers regional balance-of-payments deficit. To relieve unemployment in the East the central banks in both countries would have to expand the national money supplies or, to prevent inflation in the West, contract the national money supplies. (Meanwhile the Ca
29、nada-U.S. exchange rate would move to preserve equilibrium in the national balances.) Thus unemployment can be prevented in both countries, but only at the expense of inflation; or, inflation can be restrained in both countries but at the expense of unemployment; or, finally, the burden of adjustmen
30、t can be shared between East and West with some unemployment in the East and some inflation in the West. But both unemployment and inflation cannot be escaped. The flexible exchange rate system does not serve to correct the balance-of-payments situation between the two regions (which is the essentia
31、l problem), although it will do so between the two countries; it is therefore not necessarily preferable to a common currency or national currencies connected by fixed exchange rates. Regional Currency Areas and Flexible Exchange Rates The preceding example does not destroy the argument for flexible
32、 exchange rates, but it might severely impair the relevance of the argument if it is applied to national currencies. The logic of the argument can in fact be rescued if national currencies are abandoned in favor of regional currencies. To see this suppose that the world reorganizes currencies so tha
33、t Eastern and Western dollars replace Canadian and U.S. dollars. If the exchange rate between the East and the West were pegged, a dilemma would arise similar to that discussed in the first section. But if the East-West exchange rate were flexible, then an excess demand for lumber products need caus
34、e neither inflation nor unemployment in either region. The Western dollar appreciates relative to the Eastern dollar, thus assuring balance-of-payments equilibrium, while the Eastern and Western central banks adopt monetary policies to ensure constancy of effective demand in terms of the regional cu
35、rrencies, and therefore stable prices and employment. The same argument could be approached from another direction. A system of flexible exchange rates was originally propounded as an alternative to the gold standard mechanism, which many economists blamed for the worldwide spread of depression afte
36、r 1929. But, if the arguments against the gold standard were correct, then why should a similar argument not apply against a common currency system in a multiregional country? Under the gold standard, depression in one country would be transmitted, through the foreign-trade multiplier, to foreign co
37、untries. Similarly, under a common currency, depression in one region would be transmitted to other regions for precisely the same reasons. If the gold standard imposed a harsh discipline on the national economy and induced the transmission of economic fluctuations, then a common currency would be g
38、uilty of the same charges; interregional balance-of-payments problems are invisible, so to speak, precisely because there is no escape from the self-adjusting effects of interregional money flows. (It is true, of course, that interregional liquidity can always be supplied by the national central ban
39、k, whereas the gold standard and even the gold exchange standard were hampered, on occasion, by periodic scarcities of internationally liquid assets; but the basic argument against the gold standard was essentially distinct from the liquidity problem.) Today, if the case for flexible exchange rates
40、is a strong one, it is, in logic, a case for flexible exchange rates based on regional currencies, not on national currencies. The optimum currency area is the region. A Practical Application The theory of international trade was developed on the Ricardian assumption that factors of production are m
41、obile internally but immobile internationally. Williams, Ohlin, Iversen, and others, however, protested that this assumption was invalid and showed how its relaxation would affect the real theory of trade. I have tried to show that its relaxation has important consequences also for the monetary theo
42、ry of trade and especially the theory of flexible exchange rates. The argument for flexible exchange rates based on national currencies is only as valid as the Ricardian assumption about factor mobility. If factor mobility is high internally and low internationally, a system of flexible exchange rat
43、es based on national currencies might work effectively enough. But if regions cut across national boundaries or if countries are multiregional, then the argument for flexible exchange rates is only valid if currencies are reorganized on a regional basis. In the real world, of course, currencies are
44、mainly an expression of national sovereignty, so that actual currency reorganization would be feasible only if it were accompanied by profound political changes. The concept of an optimum currency area therefore has direct practical applicability only in areas where political organization is in a st
45、ate of flux, such as in ex-colonial areas and in Western Europe. In Western Europe the creation of the Common Market is regarded by many as an important step toward eventual political union, and the subject of a common currency for the six countries has been much discussed. One can cite the well-kno
46、wn position of Meade (61, pp. 385-386), who argues that the conditions for a common currency in Western Europe do not exist, and that, especially because of the lack of labor mobility, a system of flexible exchange rates would be more effective in promoting balance-of-payments equilibrium and intern
47、al stability; and the apparently opposite view of Scitovsky (96, chap. 2),8 who favors a common currency because he believes that it would induce a great degree of capital mobility, but adds that steps must be taken to make labor more mobile and to facilitate supernational employment policies. In te
48、rms of the language of this paper, Meade favors national currency areas whereas Scitovsky gives qualified approval to the idea of a single currency area in Western Europe. In spite of the apparent contradiction between the two views, the concept of optimum currency areas helps us to see that the con
49、flict reduces to an empirical rather than a theoretical question. In both cases it is implied that an essential ingredient of a common currency, or a single currency area, is a high degree of factor mobility; but Meade believes that the necessary factor mobility does not exist, whereas Scitovsky argues that labor mobility must be improved and that the creation of a common currency would itself stimulate capital mobility. In other words, neither writer disputes that the optimum currency area is the region-defined in terms of internal
