I think it helps to understand that the context within which a college views a particular applicant generally (say, as one of a large number of applicants from across the country) is bound to be different from the context within which such applicant is viewed locally (say, as one of a small number of applicants from a particular high school or geographic region). Moreover, the context within which an applicant is viewed by one college is also bound to be different from the context within which that same applicant is viewed by another college, given not only that applicant groups are not completely identical from one college to another but also that the sizes of their respective freshman classes may vary considerably. Context can often explain why an applicant is offered admission by one college and not another.
There is no single scale (or at least none that makes sense to me) against which colleges are able to precisely rank-order applicants from one to whatever number. There are simply too many variables involved. For instance, similar grade point averages may represent quite different levels of achievement across thousands of high schools or even across different departments within the same school. And think of the number of possible combinations of standardized test scores. That is why we treated each application individually at Princeton during my time as Dean of Admission there, and why we made every effort to take into account the enormous variation in academic and extracurricular opportunities from one school to the next, from one community to the next, from one state to the next, and from one country to the next. Experience suggests that excellence does not come in uniform dimensions.
My next post will discuss selective colleges.