What is CSR?

The Cohort Survival Ratio (CSR) is an enrollment projection method which essentially compares the number of students in a particular grade to the number of students in the previous grade during the previous year.  Ratios are computed for each grade progression and are then used to project future enrollments.

The ratio indicates whether a change in the number of students is indicative of enrollment that is stable, increasing, or decreasing.  A ratio of one indicates stable enrollment, less than one indicates declining enrollment, while greater than one indicates increasing enrollment.  If, for example, a school district had 100 fourth graders and the next year only has 95 fifth graders, the CSR would be 0.95. 

Is any district a candidate for using the Cohort Survival Ratio?

CSR is most applicable for districts that have relatively stable increasing or decreasing trends without any major change in these trends from year to year. In school districts that are encountering rapid growth due to new residential developments, CSR must be modified and supplemented with additional information to ensure accuracy. 

Is the cohort ratio for each grade based on just the last cohort or an average of past cohorts?

Calculating a single cohort ratio per grade to help project future enrollments is not typically performed since an “aberration year” can heavily impact the accuracy of the projections. Therefore, an average cohort ratio of the past three, four, or five years is used to smooth out any irregularities that may exist in the data set.

How are future kindergarten students projected?

To project kindergarten enrollment, birth data, lagged five years behind its respective kindergarten class, is used to calculate a cohort ratio. Birth data is obtained from the Department of Health and Vital Statistics at the state level as more accurate records are kept as compared to those at the local level.