The striking increase in average life expectancy during the twentieth century rates as one of the major events of our time. We are in the midst ofa social revolution-one rooted not in a new ideology, but in our changing population pat terns. For the first time in human history, infants in fortu nate nations like ours can expect to live well into their seventies and beyond. This demographic revolution increases pressure on re sources, as it also creates further social change and new opportunities for older persons. Such rapid changes have left most people "living in the past," with their...