This kind of makes sense for the vocational courses you mention but only when students follow the expected path. If a medical student fails out, they may strugg

This kind of makes sense for the vocational courses you mention but only when students follow the expected path. If a medical student fails out, they may struggle to pay back the large loan taken out against their future earnings. The same is true if they pass but don’t want to be a doctor. I studied mathematics at university and if you look at the typical student entering undergrad at my university, there was a high chance they would go into further education after the degree, and a somewhat smaller chance they would become an academic (though this is the outcome the university was focusing on). There was a reasonable chance they would go on to a reasonably ordinary middle class job, and a small but significant chance they would go into a highly paid field like investment banking. It seems it would be terrible for those incoming students to take out loans against their expected future income because the average is pushed up by a small proportion of high-paying careers, while many students may choose to go into lower paying jobs (e.g. being phd students). The problem is that the greatest burden falls on those who fail to meet the income expectations. I think such a system is regressive, at least in the technical sense. Obviously with the hind sight of being someone with a reasonable amount of success, one might want to have had a system like the one you describe, but I think I wouldn’t want my friends who e.g. went on towards academia to have suffered such a system, and perhaps the pressure of needing to find work to repay loans would have led to a worse outcome for me. I think I would want a system where the risks are socialised to at least a large extent. But I sympathise that some people don’t like the idea of others going off to get certain degrees that don’t really lead to improved financial outcomes, and the more serious issue of not having a way to incentivise certain courses[1]. In the uk we have a bizarre system of “loans” where if you are from a wealthy family you pay upfront for university, if you are not so wealthy the government pays for your tuition (for a certain amount of time) and provides money to cover living expenses as a “loan”, and if you are more poor the government (and if you’re lucky your university) will provide extra money towards your living costs as a grant. The “loan” accrues interest at a somewhat high rate (that depends on how much money you make) but isn’t really like a loan because it is paid back based on income (one pays 9% of gross monthly income above a threshold of about £20k/12) and written off after 30 years. This means that while people who don’t earn so much money don’t have an impossible burden after university, it is people with middle incomes who end up paying back the most in absolute terms (e.g. getting the balance down to 0 just before the 30 years is up and paying a lot of interest) while those with high incomes can quickly pay off the loans without paying so much interest and then enjoy an effective 10% pay rise. It seems this system is also somewhat regressive.