A “fundamental disequilibrium” exists when outward payments have a continuing tendency not to balance inward payments. A disequilibrium may occur for various reasons. Some may be grouped under the head of structural change (resulting from changes in tastes, habits, institutions, technology, etc.). A fundamental imbalance may occur if wages and other costs rise faster in relation to productivity in one country than they do in others. Imbalance may also result when aggregate demand runs above the supply potential of a country, forcing prices up or raising imports. A war may have a profoundly disturbing effect on a country’s economy.

In the traditional “classical” view no intervention by the authorities was necessary to maintain external equilibrium, except for their readiness to convert currency into gold (or silver) upon demand. The system was supposed to work automatically. If a country had a deficit, gold would flow out, and the consequent reduction in the domestic money supply would cause prices to move downward. This would stimulate exports and tend to reduce imports. The process would continue until the deficit was eliminated. Classical doctrine did not embody a clear-cut theory about international capital movements. It was usually assumed that the trade balance (more strictly, balance on goods and services) would be tailored to accommodate any capital movement that occurred. Thus, if the country was exporting capital, gold flows would cause prices to move to such a level that exports minus imports would be equal to the capital flow; equilibrium in the overall balance was automatically secured.

In due course the classical scheme of thought came under criticism. Some critics asked if an outflow or inflow of specie would necessarily have a sufficient effect on the price level to ensure an equal balance of payments. More important, a reduction in the money supply, it was pointed out, might have a side effect on the level of economic activity. Some critics went further and argued that this side effect would be stronger than the effect on prices to such a degree as to cause unemployment to rise to an undesirable level.

The belief grew that positive action by governments might be required as well. The doctrine was first related to monetary policy in particular. The idea was that interest-rate adjustments should be combined with open-market operations by a central bank to ensure that the domestic money supply and borrowing facilities were conducive to external long-period equilibrium. After World War II the idea came to be widely held that government budget policy (usually called fiscal policy) should be brought in to assist monetary policy. For instance, if aggregate domestic demand was running so high as to cause rising prices, this should be reduced both by having a tight monetary policy and by increasing taxation more than expenditure or reducing expenditure without reducing taxation. The correct apportionment of this task between the monetary and fiscal arms is still a subject of discussion.

Nor is there yet agreement about the scope of these policies or their ability to secure fundamental equilibrium in all cases. There is probably agreement that when overall demand is running in excess of the supply potential of the economy, it should be reduced by monetary and fiscal policies. There is difference of opinion, however, as to whether the reduction of aggregate demand will bring external payments into balance in all cases. For instance, a country may have a deficit owing to some underlying economic change (such as a shift in the pattern of world trade), even if domestic demand is not above the supply potential and prices are not rising. In this case, policies designed to reduce domestic demand (commonly called deflationary policies) would cause unemployment. Some hold that, if there is an external deficit, deflationary policies should be pursued to whatever extent may be needed to eliminate the deficit. Others hold that such a policy is socially unacceptable.

Opinions differ also about how deflationary measures work to improve the external balance. Some hold that they work mainly by reducing domestic activity and thereby the amount of imported materials that a country needs and the amount of income that people can afford to spend on imported goods. If this were the whole effect of a deflationary policy, it would improve the external balance only in proportion to the amount by which it increases unemployment. Those who hold that this is the only manner in which deflation affects the external balance are especially opposed to relying on deflationary policies alone to eliminate a deficit in conditions in which aggregate domestic demand is not running above the supply potential. Some hold that a reduction of home demand also helps because it makes producers look around more eagerly for export markets (and increase their selling efforts in the home market). This appears to be doubtful, however. There is further disagreement on the extent to which deflationary policies influence the course of prices. If aggregate demand is running above the supply potential of the economy, it is highly probable that deflationary policies will slow the increase of prices and thus make a country more competitive with foreign suppliers. There is not the same agreement about the effects when demand is initially running below the supply potential of the economy. Some hold that a deflationary policy, if pushed hard enough, will infallibly slow up price increases and so help the country’s external balance. Others hold that it will not, and some even argue that higher interest rates and higher taxes (weapons of deflation) can cause prices to rise. Thus, it is not absolutely clear that monetary and fiscal policies will in all cases suffice to cure an external deficit, at least without socially unacceptable results.

There is also the opposite case of countries with a trade surplus. It is clear that these countries will be unwilling to encourage policies that cause domestic prices to rise. Price inflation is a social evil and politically unpopular.

In the case of surplus countries, the same distinction must be made between the situation in which aggregate demand is fully up to or above the supply potential of the economy and that in which it is not. In the former case a further increase in demand would almost certainly have an inflationary effect; accordingly, surplus countries in this condition will be unwilling to use monetary and fiscal policies to eliminate their external surpluses. On the other hand, if aggregate demand is running below supply potential, then a surplus country might reasonably be asked to increase aggregate demand by monetary and fiscal policies on the view that the increase will not cause inflation but will tend to remove the external surplus by inducing more imports and possibly causing producers to be less active in their selling efforts abroad.