It would require a decent survey to see where people in Oxford want to fly.
This has already been done but is kept as an internal document that was not published to my knowledge. From memory, Schipol came out as the number one international destinaton, followed by Dublin I think. Edinburgh was by far the most in demand domestic route, which is why the airport persuaded Varsity Express to consider Edinburgh instead of Cambridge (though that was before they realised they were dealing with Martin Halstead again).