Revised NSC Model Still Shows Greater Enrollment Declines Than Does IPEDS

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In early January I noted a growing discrepancy between the US higher education enrollment reporting between National Student Clearinghouse (NSC) and the Department of Education’s Integrated Postsecondary Education Data System (IPEDS). The issue is not that there is a discrepancy – different data methods after all – but that there is a growing discrepancy. I subsequently interviewed Doug Shapiro, executive research director for NSC, and described the data methods and possible explanations for the growing discrepancy. [full-page audio link]

Valid Identifiers – When students do not have a valid identifier associated to help with unduplicated counts, NSC has chose to exclude them from Enrollment Estimates reporting. Historically the majority of these students were international, but for reasons that NSC researchers do not understand, the number of domestic students without unique identifiers has been growing, which could also explain a lot of the growing discrepancy. [snip]

The two best guesses at explanations for the growing discrepancy in enrollment reporting are therefore 1) growing number of students reported without a valid identifier and 2) growing number of students in non-degree programs. We should find out a lot more with the Fall 2022 report. The former would overstate enrollment declines, and the latter is just confusing.

NSC has now released its Fall 2022 Current Term Enrollment Estimates, removing the issue about missing valid identifiers and revising numbers back to 2017, and answer is surprising to me. The short version is that the absolute numbers are now closer to IPEDS numbers, but the discrepancy is still growing – perhaps even more than with the previous model. The new NSC model shows a four-year decline (2017 to 2021) of 8.3% compared to 5.3% for the IPEDS model. Note that I am using the IPEDS numbers called out in previous blog posts here.

Revised NSC Model

NSC’s latest Current Term Enrollment Estimates were presented in a new style, with interactive Tableau graphics and a downloaded data appendix. The headlines for this release last week were that enrollment declines are stabilizing (smaller losses) and that freshmen enrollment actually increased year-over-year. There are plenty of news sources running with this story.

Before getting to our topic of discrepancies, I’d like to note that the NSC data and reporting are getting better and better. I like the new interactive format, and I appreciate the willingness to publicly correct mistakes and improve data categorizations.

True to its word, NSC also revised their data methodology and provided prior year revisions back to 2017, as described in the methodology notes.

6. Student Identifiers: Past editions of this report omitted students without valid identifiers in the Clearinghouse data. We have included these students for the first time here. This is a relatively large change as these students increased steadily, from 4.2 percent (in 2017) to 6.4 percent (in 2022) of the total headcounts.

Changing Enrollment Models

To visualize the effect of this new NSC model in comparison to IPEDS – in order to get a better sense on the real enrollment declines nationwide – I am showing the previous NSC model for fall 2012 – 2021, the revised NSC model for fall 2017 – 2022, and the latest IPEDS model for fall 2012 – 2021. Alongside I am showing the discrepancy (essentially IPEDS fall numbers minus the previous NSC numbers for that year or the revised numbers for that year).

From fall 2017 to fall 2021 (the period with all data models showing enrollment numbers), the old NSC model had a decline of 1.5 million students, the new NSC model had a decline of 1.66 million, while IPEDS only had a decline of 1.05 million. The largest difference between NSC models occurred in 2018, but there is not enough data to see if that was an outlier.

comparing US higher ed enrollment models 2012 to 2022

In the chart, you can see the yellow discrepancy line (between IPEDS and the old NSC model) consistently growing, with the exception of 2020. The blue discrepancy line (between IPEDS and the new NSC model) starts much lower (with NSC numbers even higher than IPEDS) and then growing, again with the exception of 2020.

Percentage Declines

Looking at the reported enrollment declines on a percentage basis, we see the surprising part more clearly. With the revised model, the year-over-year enrollment changes for the new NSC model are still growing further apart from IPEDS, just as they did with the old model. In other words, the new model including students without a valid identifier did not reduce or explain most of the discrepancy, it actually made it more evident.

From fall 2017 to fall 2021 (the period with all data models showing enrollment numbers), the old NSC model had an 8.0% decline, the new NSC model had an 8.3% decline, while IPEDS only had a 5.3% decline.

comparing year-over-year US higher education enrollment changes 2012 - 2022, with previous NSC, revised NSC, and IPEDS fall enrollments

We have better data and presentation from NSC – kudos to that group – but the issue of a growing discrepancy between NSC and IPEDS enrollment numbers is still quite evident at a time where we need to understand changes to overall enrollment numbers.