ECONOMIC PSYCHOLOGY--"The notion of 'saturation' of the market is based on old-fashioned psychological assumptions which in turn rest on the analogy of biological drives: for example, if an animal is hungry, it is motivated to search for food; after it has eaten, the motive disappears. The saturation concept has resulted in dire predictions about the future of the U.S. economy [see illustration]. Some people point to the large proportion of U.S. families that already possesses major goods, such as refrigerators (over 80 per cent), and they argue that in the future sales will be limited largely to replacement needs. But social motives are different from biological ones. Fulfillment of one aim leads to striving for another."