When the IMF was established toward the end of World War II, it was based on a modified form of the gold standard. The system resembled the gold standard in that each country established a legal gold valuation for its currency. This valuation was registered with the International Monetary Fund. The gold valuations served to determine parities of exchange between the different currencies. As stated above, such fixed currencies are said to be pegged to one another. It was also possible, as under the old gold standard, for the actual exchange quotation to deviate somewhat on either side of the official parity. There was agreement with the International Monetary Fund about the range, on either side of parity, within which a currency was allowed to fluctuate.

But there was a difference in the technical mode of operation. The service of the arbitrageurs in remitting physical gold from country to country as needed was dispensed with. Instead the authorities were placed under an obligation to ensure that the actual exchange rates quoted within their own territories did not go outside the limits agreed upon with the International Monetary Fund. This they did by intervening in the foreign exchange market. If, for instance, the dollar was in short supply in London, the British authorities were bound to supply dollars to the market to whatever extent was needed to keep the sterling price of the dollar from rising above the agreed-upon limit. The same was true with the other currencies of the members of the International Monetary Fund. Thus, the obligation of the monetary authorities to supply the currency of any Fund member at a rate of exchange that was not above the agreed-upon limit took the place of the obligation under the old gold standard to give actual gold in exchange for currency.

It would be inconvenient for the monetary authorities of a country to be continually watching the exchange rates in its market of all the different currencies. Most authorities confined themselves to watching the rate of their own currency against the dollar and supplying from time to time whatever quantity of dollars might be required. At this point the arbitrageurs came into service again. They could be relied upon to operate in such a way that the exchange rates between the various currencies in the various foreign exchange markets could be kept mutually consistent. This use of the dollar by many monetary authorities caused it to be called a currency of “intervention.”

The official fixing of exchange rates as limits on either side of parity, outside of which exchange-rate quotations were not allowed to fluctuate, bears a family resemblance to the gold points of the old gold standard system. The question naturally arose why, in devising a somewhat different system, it was considered desirable to keep this range of fluctuation. In the old system it arose necessarily out of the cost of remitting gold. Since there was no corresponding cost in the new system, why did the authorities decide not to have a fixed parity of exchange from which no deviation would be allowed? The answer was that there was convenience in having a range within which fluctuation was allowed. Supply and demand between each pair of currencies would not be precisely equal every day. There would always be fluctuations, and if there were one rigidly fixed rate of exchange the authorities would have to supply from their reserves various currencies to meet them. In addition to being inconvenient, this would require each country to maintain much larger reserves than would otherwise be necessary.

Under a system of pegged exchange rates, short-term capital movements are likely to be equilibrating if people are confident that parities will be maintained. That is, short-term capital flows are likely to reduce the size of overall balance-of-payments deficits or surpluses. On the other hand, if people expect a parity to be changed, short-term capital flows are likely to be disequilibrating, adding to underlying balance-of-payments deficits or surpluses.

Commercial banks and other corporations involved in dealings across currency frontiers are usually able to see some (but not necessarily all) of their needs in advance. Their foreign exchange experts will watch the course of the exchanges closely and, if a currency is weak (i.e., below parity), advise their firms to take the opportunity of buying it, even if somewhat in advance of need. Conversely, if the currency is above parity but not expected to remain so indefinitely, they may recommend postponing purchases until a more favourable opportunity arises. These adjustments under the influence of common sense and self-interest have an equilibrating influence in foreign exchange markets. If a currency is temporarily weak, it is presumably because of seasonal, cyclical, or other temporary factors. If on such an occasion private enterprise takes the opportunity to buy the currency while it is cheap, that tends to bring demand up to equality with supply and relieves the authorities from the need to intervene in order to prevent their currency from falling below the lower point whenever there is a temporary deficit in the balance of payments. As previously noted, when confidence in the fixed parity exchange rate drops and market participants expect a change in parity, short-term capital movements may be disequilibrating. (See below Disequilibrating capital movements.)

Another equilibrating influence arises from the movements of short-term interest rates. When the authorities have to supply foreign currencies in exchange for the domestic currency, this causes a decline in the money supply in domestic circulation—unless the authorities deliberately take offsetting action. This decline in the money supply, which is similar to that occurring under the gold standard, tends to raise short-term interest rates in the domestic money market. This will bring an inflow of money from abroad to take advantage of the higher rates or, what amounts to the same thing, will discourage foreigners from borrowing in that country’s money market since borrowing will have become more expensive. Thus, the interest-rate differential will cause a net movement of short-term funds in the direction required to offset the temporary deficit or, in the opposite case, to reduce a temporary surplus that is embarrassing to others. It must be stressed again that this equilibrating interest-rate mechanism implies confidence that the parity will not be altered in the near future.

The helpful movement of interest rates may be reinforced by action of the monetary authorities, who by appropriate open-market operations may cause short-term interest rates to rise above the level that they would have attained under market forces and thus increase the equilibrating movement of short-term funds. The Bank of England provided the most notable example of the smooth and successful operation of this policy under the old gold standard during many decades before World War I.