INFLATION: In the 1970s the prices of most things Americans buy more than doubled. Such a general increase in prices is called inflation. Prices of selected goods may increase for reasons unrelated to inflation: the price of fresh lettuce may rise because unseasonably heavy rainfall in California has ruined the lettuce crop, or the price of gasoline may rise if the oil-producing countries set a higher price for oil. During inflation, however, all prices tend to rise. Over the last 400 years there have been many periods of inflation. In the 16th century, when the Spaniards began bringing back gold and silver from the New World, prices in Western Europe mov