Migration data suggest an evolutionary process in which central cities attract high status migrants when cities are relatively small, attract migrants less as they grow, and then again become attractive. Large northern cities may currently be in the middle stage. (Author/MJL)

The social policy implications of demographic trends are examined, to help policy makers anticipate future needs for services with greater accuracy. Crises such as energy needs and social security financing illustrate the need for greater recognition of the time dimension of public policy. Many of our most difficult problems, if they are to be…