Although all recorded societies have contained a few people of extreme old age, they have been the exception rather than the rule. The possibility of one fifth of the total population in retirement from active employment would have been unthinkable at the beginning of the twentieth century and even social planning in the 1970s had made no adequate provision for a society in which one in every twenty-five people would be over seventy-five and one in every hundred over eighty-five within less than a decade.