The ranking many families trust most was never built for them. The Academic Ranking of World Universities began in Shanghai in the early 2000s as a tool to benchmark China’s universities against global competitors for a national modernization program. It measures research output: Nobel laureates, papers in Nature and Science, citations. Of the world’s roughly 18,000 institutions, it ranks 1,000.

Today admissions consultants cite that same ranking to advise students who have no intention of a research career. It is the wrong tool applied to an entirely different question.

National rankings like U.S. News have a different flaw. The problem is not that any single criterion is wrong. It is that crushing many criteria into one number destroys information while manufacturing false precision. As Goodhart’s Law warns, when a measure becomes a target, it stops being a good measure.

Ratings, which describe a school on specific dimensions, can genuinely help. Rankings, which collapse everything into a single place in line, mostly mislead. Knowing the difference changes which schools you take seriously.

This is Chapter 21 of the book. Read the full case in the book, or compare schools on investment terms in the model.

Read next: Is College Worth It? The argument in full, or when a degree costs more than it returns in this breakdown.