High school graduates in regions where UChicago is a desirable and known brand (Northeast, Midwest) will decline and grow where it is not as known or desired (West, South). Based on this, the higher risk is not in alienating current applicants (there is a ton of them) but in the obvious handicap in attracting future applicants.
The 2016 study, “Knocking at the College Door,” suggests the number of graduates will plateau now at about 3.5 million for years before declining. Declines are concentrated in the Midwest and Northeast, while the South and West continue to expand.
Well certainly a strong marketing campaign and (like it or not) retaining a top 5 position in USNWR will move UChicago from being well known regionally to well known nationally (among high school seniors) which in turn enables strong applicants to be evaluated for admission.
My son received so much marketing from U Chicago, including a t shirt. He applied EA and was deferred. In retrospect, he wishes they hadn’t sent all the bling. He is from a rural county in the South, small high school and the only NMSF in his graduating class of 331.