Still a Small World?
University Course Enrollment Networks before and during the COVID-19 Pandemic

In normal times, the network ties that connect students on a college campus are an asset; during a pandemic, they can become a liability. Using prepandemic data from Cornell University, Weeden and Cornwell (2020) showed how co-enrollment in classes creates a "small world" network with high clustering, short path lengths, and multiple independent pathways connecting students.Using data from the fall of 2020, we assess how the structure of the co-enrollment network changed as Cornell, like many other institutions of higher education, adapted to the pandemic by adopting a hybrid instructional model. We find that under hybrid instruction, not only is a much smaller share of students in the face-to-face network, but the paths connecting student pairs in the network lengthened, the share of student pairs connected by three or fewer degrees of separation declined, clustering increased, and a greater share of co-enrollment ties occurred between students in the same field of study. The small world became both less connected and more fragmented.