Although realized trade flows and the consequent changes in currency holdings will affect the current spot exchange rate, the expected future change in the spot rate will be affected by expectations regarding the future balance of trade and its implied currency holdings. An important aspect of this analysis is that changes in the future expected value of a currency can have an immediate impact on current spot rates. For instance, suppose there is a sudden change in the world economy that leads to expectations of a larger trade deficit in the future, say, an international oil cartel develops and there is an expectation that the domestic economy will have to pay much more for oil imports. In this case forward-looking individuals will anticipate a decrease in domestic holdings of foreign money over time. This, in turn, will cause expectations of a higher rate of appreciation in the value of foreign currency, or a faster expected depreciation of the domestic currency. This higher expected rate of depreciation of the domestic currency leads to an immediate attempt by individuals and firms to shift from domestic into foreign money. Because, at this moment, the total stocks of foreign and domestic money are constant, the attempt to exchange domestic for foreign money will cause an immediate appreciation of the foreign currency to maintain equilibrium, and so the existing supplies of domestic and foreign money are willingly held.