Discrepancy in Reported US Higher Ed Fall Enrollment Declines

With the release of the Fall 2021 enrollment data from the US Department of Education’s IPEDS system, I had planned a post showing a comparison of three commonly-used data sources to help provide context, but as I looked further there seems to be a significant discrepancy between the National Student Clearinghouse (NSC) enrollment reports and the official IPEDS data release. The NSC data show larger enrollment declines for all but one year in the past decade (2020), leading to an estimate of a 12.0% decline (2.4 million) from Fall 2012 – 2020, when the IPEDS fall numbers show an 8.0% decline (1.7 million) in that time period.

While both data sources show decade-long enrollment declines, that difference of 12.0% vs 8.0% has big implications, and we need to understand why.

Data Sources

The two best sources for enrollment data for US Higher Education are the Department of Education’s IPEDS data set and the National Student Clearinghouse (NSC) reports. The NSC shares the Current Term Enrollment Estimates reports for both Fall and Spring periods.

  • IPEDS: Official data reports based on census with nearly all institutions reporting; best for historical data but usually 12 – 18 months after the terms has ended; data is fully reported across sectors and institutions, allowing independent analysis of results

  • NSC Current Term: Based on survey with “97 percent of the total enrollments at Title IV, degree-granting institutions in the U.S.” reporting; best for summarizing the term just completed in a timely manner; data is partially reported without the ability for independent analysis

Because the NSC data are more timely, those numbers tend to get reported in the media. Consider two articles based on Fall 2019 data (which you’ll see below as the biggest discrepancy):

Once the IPEDS data for Fall 2019 came out, it showed a 0.1% decline of approximately 20,000 students.

View of Three Models

But when we look back over the past decade, for an unexplained reason the numbers are diverging. Given the ongoing enrollment reporting on this blog based on annual IPEDS data, I am showing three data models below:

  • The National Student Clearinghouse (NSC) fall enrollment data based on annual reports

  • The PhilOnEdTech (POET) model we’ve developed with IPEDS data

  • The IPEDS Digest of Education Statistics (DES) report from February 2022, from table 303.10

Even with IPEDS data, there are some differences between the POET and DES versions, partially based on the inclusion or exclusion of less-than-two-year sectors and provisional vs. final reports. These differences are on the order of 30 to 50 thousand students. The NSC data differ by a larger amounts that increase every year – from 500 thousand to 1.35 million students.

The biggest difference in reporting that I am aware of is that NSC reports unduplicated headcounts.

Moreover, since the Clearinghouse collects data at the student level, it is possible to report an unduplicated student headcount, which avoids doublecounting students who are simultaneously enrolled at multiple institutions.

I can see this method leading to smaller enrollment totals each year, but I have trouble believing that the number of students attending multiple institutions can explain the difference in trends and year-over-year changes. If it does, that is a story worth reporting on its own. [See update below – this could be the main explanation.]

When looking at percent changes year-over-year (YoY), NSC shows oft-reported declines that are much higher for every year except 2020.

Comparing year over year changes in US higher education fall enrollment models 2012 to 2021

I do not know the reason for these differences, and NSC is notoriously unresponsive to requests to clarify data. For now, the issue is that there is a significant difference in reporting from NSC about enrollment declines when compared to official IPEDS numbers. While IPEDS data come out with a delay, those numbers should be more accurate as they are based on official school reporting with no model estimations. If someone can shed light on this discrepancy, let me know privately or in the comments; if and when I find out more, I’ll report it here.

Update 1/3: If you look at the 12-month unduplicated headcount enrollment data from IPEDS, the issue of unduplicating student counts may explain a lot of the discrepancy. Note that in this table, the change from 2018-19 to 2019-20 was roughly 208 thousand students, which lines up with NSC differences for Fall 2019. And note the change from 2012-13 to 2020-21 was more than 2.7 million students, again lining up with NSC. An unreported story could be the changing mix of students enrolled at a single institution vs. multiple institutions. Two sections of the text above have been updated to highlight the discrepancy vs. assuming that NSC is overstating declines.

IPEDS 12-month unduplicated student headcount table