No, it doesn't. I thought this was clear from context, but: these are not constants. They are functions of many, many variables, many of which are probably sha

No, it doesn't. I thought this was clear from context, but: these are not constants. They are functions of many, many variables, many of which are probably shared; and probably also their dynamics are non-trivial. For instance, changes to prices could be perfectly captured because all three variables are functions of price, and each of them probably has at least a first price derivative. I actually talk about this in terms of the model in my post, so I'm not sure where you got the idea that the model can't capture price change. Also, demand for higher education is fairly inelastic compared to other variables within fairly coerce regions, so sacrificing fine-grained analysis of demand in exchange for more important variables isn't the worst exclusion.