This paper examines the changing demographics of American society and the impact of these changes on higher education. Discussions include a historical background of early American demography, the building and expansion of the population base, and census changes through various generations of the baby boom years and beyond. Next, the report examines efforts in forecasting older student enrollment which enable state and local forecasters to estimate enrollment numbers and institutional market share. Also discussed are the development and use of forecasting models, such as the Older Cohort Participation Matrices (OCPM), and the various data collection sources that are used by the U.S. Census Bureau. Tables of data show population projections from 1990-2080, U.S. population by selected age cohorts, older student population bases from 1921-1986, the older student market base/projected older population cohorts matrix from 1980-1998, and the older student enrollment forecasts/older student enrollment by cohort from 1980-1998. Finally, a review is made of the many factors that affect student population projections, both external and those stemming from the students and institutions themselves, followed by a discussion of the implications these factors will have on colleges and universities as they prepare themselves for this market and attempt to participate in it. Contains 14 references. (GLR)