Well, if you're going to throw down the gauntlet like that Mr. Caplan, how can I resist! I began by actually looking at this authors spreadsheets, then looking at their claims, and ultimately, I downloaded a copy of their book[0] to review what that book says. So here's the info:

The fundamental claim of the book is that currently, the "western education model" is not (really) about skill accumulation or increasing the utility that an individual can provide society. Instead, our current "western education model" is about signalling a workers productivity to potential employers. That is the thesis of the book, as spelled out in the introduction of the book.

I downloaded the spreadsheets[1] that the author talked about.[2] I've reviewed them for about an hour, in between reading, and my take is that no one cares about the spreadsheets because they're INCREDIBLY basic. In short, the spreadsheets are a collection of statistics about the outcomes of students who complete various levels of education. It shows income earned per year of education completed, for a number of different hypothetical students (excellent students, poor students, etc). The numbers aren't particularly shocking on their face, and the spreadsheets don't have anything like a single cell on the first sheet labeled "SMOKING GUN, WOW" to catch your attention. Instead, the general point from the statistics is that we see unusual jumps in the expected compensation of students at various "round numbers", such as jumps at 12 years of education completed (finished high school), and 16 years of education completed (finished undergraduate). The author seems to take these as strong proof for their original point that the value of education is in "signalling", not in increasing a persons ability.

My fundamental issue with this is that this data, as I've read it, could be understood a different way than "education is just a social signal". By my reading, this data could just as well be "western hiring markets are wildly under-valuing the abilities of folks who narrowly miss common landmark achievements". I believe that's also an idea worthy of study, but I don't see it addressed in any of the authors writing, or in the book.

[0] - https://eddierockerz.files.wordpress.com/2020/12/the-case-ag...

[1] - https://econfaculty.gmu.edu/bcaplan/compensationcleanfinal.x...

[2] - https://www.econlib.org/archives/2014/06/embarrass_me_no.htm...