Admission rates are heavily dependent on how easy it is to apply, how many times you're allowed to apply, how likely a student thinks their chances are, basically heavily dependent on the college application process, which is very different in different countries. E.g, I think Indian IITs have <1% acceptance rates but you probably don't have to shell over a $100 to apply.
That may be it, under-supply of schools. What's required there besides perfect, or near perfect SAT scores?
Also, I've always wondered why so few Americans decide to study in Europe. I understand some might not be able to afford the remote study, but this doesn't explain everything. Language is not a problem, every top university offers all, or almost all master's level courses also in English.
I imagine this is a generalisation, some of the elite universities in Europe require 2 year prep programs before you can even apply (e.g. France) which doesn't sound easier than top American ivies?
That's quite some difference, especially if we consider that Harvard has special tracks for legacies and various others. What's the real admission rate? 2%?
For other European unis I don't know what exactly the criteria are for being elite.
I've always had a problem with admission rates, since they obviously depend on self-selection (and supply of schools).
Germany is a good example here, they have a wide spectrum of schools starting already past primary education (around 10 years old). Many of those schools, those of the "mid" and especially "lower" rank do not bash into children's heads that they absolutely must go to a good university or they will be a failure. As a result those kids do not apply there, instead they go into internships and get a job. Overall there is a continuum that a) reduces pressure on people that probably shouldn't study medicine or law, b) gives better education to talented children by putting them together in more aligned groups.
Crucially, the admission to those schools past age of 10 is not zip-code based. Admitting children by zip-code past the very first school where you learn how to sit, read, write and multiply numbers is nonsense.
A process like this will result in a higher university admission rate, all else being equal, including the "true difficulty" of getting into a specific university.
Just go with national / global pool for the denominator. There are about 4 million high school graduation age children in the usa. Probably about 80-100 million world wide. About 20000 ivy league spots per year. So you need to be about one of 5 in a 1000 in the usa. Maybe 1 in a 1000 globally after adding global equivalents of us Ivy League schools. basically top 0.1 to 0.5 %.
The admission rate alone doesn't tell you if, as a candidate, I have more chances of getting into this or that university, because it doesn't say anything about who applies. There might big differences between the pools of applicants.
Oxbridge's admissions rates are not the lowest in the UK; schools no one outside the UK has heard of, like Warwick, have the lowest, and their admissions rates are still two to three times higher than the Ivies'. In many countries, universities admit all applicants that meet the qualifications. An example is Switzerland, where ETH Zurich—by every measure, among the world's finest universities—admits every Swiss with a Matura (university-track high school diploma) who applies.
People do get kicked out of ETH, the selection is after admission, not before (as opposed to e.g. most US universities), at least when you enter right after high school. So it's not comparable. Granted it's still easier to "get into", but that won't get you much if you can't graduate.
Another thing to consider is that the pool of applicants might be different between universities. 1% admission rate tells you a very different story whether 100% or 10% were decent applicants in the first place.