I often find such stats interesting, but it’s important to look at why, rather than just look at the absolute number. For example, some example graduation rates from selective colleges in the latest IPEDS (2019-20) are below. I expect some of them changed by +/-1 in the 2020-21, like Chicago did.
4-year, 5-year, and 6-year Grad Rates
Notre Dame – 91%, 95%, 96%
Georgetown – 91%, 94% 95%
Princeton – 90%, 97%, 98%
Chicago – 90%, 93%, 95%
Bowdoin – 89%, 94%, 95%
WUSTL – 89%, 94%, 95%
Yale – 88%, 95%, 97%
MIT – 87%, 94%, 95%
Cornell – 87%, 93%, 95%
Penn – 86%, 94%, 96%
Berkeley – 76%, 90%, 93%
Stanford – 73%, 89%, 94%
GeorgiaTech – 46%, 85%, 90%
All of the listed colleges are selective enough that I expect hardly anyone is failing out and not graduating for academic reasons, yet there is still a good amount of variation in 4-year graduation rates . Some are >90% like , Notre Dame and Georgetown, while others like GeorgiaTech are under 50%. There is a correlation with selectivity, but there are many exceptions.
GerogiaTech’s 46% 4-year graduation sounds abysmal, but it makes more sense when you consider how large a portion of students pursue engineering co-ops, which is on paper a 5-year program. If a lot of students choose to pursue 5-year programs, the 4-year graduation rate will not be high. I expect being public and lower sticker price also contributes (I have previously referenced a study suggesting sticker price contributes to graduation rate after controls, perhaps due to perceived financial value of degree).
By several metrics Stanford is the most selective academic college, yet it only has a 73% 4-year graduation rate. A little over 10% of students are varsity athletes, so even if 100% of athletes did not graduate on time, it would not explain the discrepancy. I believe the low 4-year graduation rate primarily relates to Stanford’s co-terminal masters program, which is on paper a 5-year program that ~1/3 of students pursue, although it is not uncommon to take 6 years. Other more complex degree plans, co-ops, redshirting, start-up culture, and various other uncommon factors have a lesser contribution.
I’m not as familiar with Berkeley, but in addition to the above effects, I’m guessing there is a financial contribution. Berkeley has a larger portion of lower income students than any of the listed colleges, and has worse financial aid than most of them for lower income students. This combination can contribute to a larger portion of students needing to delay graduation for financial or family related issues. They also are not known for hand holding, which I expect increases risk of a few rare kids falling through the cracks.
At the other end of the spectrum, the 90+% 4-year graduation rate colleges tend to have few students pursuing co-ops, co-terms, or other more complex degree plans that take more than 4 years. They also tend to have relatively few engineering students. Notre Dame is somewhat of an exception. ~15% of students are engineering, yet they still have a >90% 4-year graduation rate. I suspect that the religious nature of the college contributes, including certain cultural aspects.
There is far less variation in 6-year graduation rates. All of the listed highly selective private colleges had a 96% +/- 2% 6-year graduation rate. One might consider this degree of difference insignificant. Stanford was lowest listed private college at 94%, likely seeing effects a rare few who take >6 years for uncommon reasons, such as more complex degree plans and/or having co-term funded via TA/RA work. For example, I did a double co-term that on paper is a 6-year plan. This double co-term was a standard program listed in the catalog at the time, to foster tech entrepreneurship. HYP all were among the highest private academic colleges at 97-98%. I expect HYP having some of the best financial aid among this group is important, so few students do not graduate for financial reasons. I expect they also have special programs to insure few students fall through the cracks for other reasons.
Regarding Chicago in particular, I don’t find the graduation percentages especially surprising. I expect Chicago has few students pursuing engineering co-ops or 5-year complex degree plans. They also offer good FA and have relatively few lower income students, so I expect few students have delayed graduation for financial reasons. This is expected to bring the 4-year graduation rate to near 90%. All the listed highly selective private colleges had a 96% +/- 2% graduation rate. I’d expect Chicago to be towards the middle of that range, perhaps a little below HYP, near some of other Ivies, so the 6-year graduation also isn’t a surprise.