IN 1966, the Johnson administration was asserting the need for a national program of housing development for the benefit of the nation’s low-income population.  Such a program in fact was enacted into federal law in 1968, setting precise numerical goals of 2.6 million units of housing a year. Of each year’s quota, 600,000 units were to be specially subsidized for occupancy by the poorest families in the nation. Twenty years later, in 1985, there is considerable agitation for a new program of affordable housing, by which its advocates mean that they want government to build housing with subsidies that will bring it within reach of the poorest people in the country.