I know nothing about economics, however I just thought I'd give you the little bit of wisdom i've learnt over 5 years at university. Firstly, you generally don't have to go into university knowing what you want to major in (or what career you want to do later).
Secondly, generally there are just basic first year subjects, and you specialise in later years. You can go to university and try the subjects, and see what you are interested in/what you like. You can also talk to other people doing that degree once you are at university and get their thoughts on subjects/future careers.
I always think its a good idea to have a bit of flexibility with university - don't go in there completely narrow minded, otherwise you may miss out on doing something amazing because you had such a narrow view of what you want to do (for example, I was set on doing ancient history after high school, didn't do many other arts subjects, kind of regretted not getting that variety in first year, and now despite all that I'm going to be a lawyer - something I never considered at the end of yr12). A lot can change between high school and university.
