Cohort crowding: how resources affect collegiate attainment

elative to cohort size) was more severe before 1970s than it was after, though the difference wasnot statistically significant.Another variable of interest in measuring higher educational attainment is enrollment.Enrollment represents an “input” to educational attainment while degrees awarded are anoutcome. Table 3 replicates the specifications in Table 2, focusing on total enrollment rather thanthe baccalaureate degree outcome. First in both periods, and particularly for the longer seriesfrom 1954-1996, the estimates for elasticity with respect to cohort size are larger for enrollment(0.89 and 0.79) than for BA degrees conferred (.71 and .62), though they are still significantlyless than one in all of the specifications.The majority of the variation in the cohort size variables employed in these specificationsis related to broad shifts in the population, with regions in the South and West growing muchmore rapidly than those in the North East and North Central. Indeed 83% of the variation in ourcohort size variable can be explained by a simple linear trend. To eliminate these secular trendsfrom the data, we have estimated specifications that include state-specific linear trends (see evennumberedcolumns of Tables 2 and 3). 16 Doing so further attenuates the link between cohort sizeand degrees awarded substantially.For the purpose of interpreting the substantial differences between results with andwithout the inclusion of state specific trends, it is important to understand the source and natureof the variation in cohort size. The cross-state variation in changes in the size of the college-agepopulation is being driven by cross-state and cross- country migration flows. 17 Presumablysecular trends in the size of the college-age population are being driven by secular trends in thelocus of economic activity in the country. Indeed, the within-state-and-year correlation betweenthe size of the 18-year old population and employment (both measured in logs) is 0.7. Aftersecular trends have been removed this correlation drops quite dramatically to between 0.1 and 0.3depending on the time period used. We suspect that even here changes in the size of the collegeagepopulation are being largely driven by changes in the location of economic activity, but thatthe timing is off – young adults migrate in response to economic opportunities, but have collegeagechildren one or two decades later.To get a perspective on the time series properties or our population measures, followingBaker, Benjamin, and Stanger (1999), we decomposed our measured into orthogonal time seriescomponents using Fourier series techniques. With 43 years of data (1954-1996), we employ the16 We also experimented with quadratic trends, which show results very similar to those presented.17 While at the national level changes in cohort size during the second half of the twentieth centurywere driven by changes in cohort fertility rates, within state and year, there is essentially no associationbetween family size and cohort size.11