As a rough estimate, I’d assume students will study for five years on average above the age of 20.
(A bachelor usually takes at least 6 semesters, plus 3 to 4 for a master. Few will do it in less, many take longer. Some bachelor graduates will not continue to pursue a Master, but 90% of university students do. Spending a semester abroad is often recommended. Average age of matura graduates is 18 or 19, but then, many are only taking up studies later. Average age of incoming students is above 20 years, same is, I believe, true for the median age. Bachelor degrees earned at an average age of approximately 25 years).
Minimum AHV contribution over five years is 496 CHF x 5 = 2480 CHF.
For this total contribution of only 2480 CHF, domestic students would receive 12.8% higher monthly pensions than their non-Swiss peers who were unable to contribute. See also, for an example calculation: „Bei einer Beitragslücke von fünf Jahren wird die Rente lebenslang um mehr als 11 Prozent gekürzt“.
The discrepancy and level of discrimination it be obvious.
On the other hand, it should be a reminder for the reader to consider making voluntary contributions (if allowed) even when not working in Switzerland.