The original article this Slate article refers to is an [article in Science Advances](http://advances.sciencemag.org/content/1/1/e1400005.full), an open-access scientific journal. The authors selected business, computer science, and history because they are three disparate fields; they figured that if they found a unifying thread across these three fields that it’s probably something that held true for academia more generally. They actually looked at 19,000 tenure-track or tenured faculty members across 461 North American departmental or school-level academic units.The [url=<a href=“http://advances.sciencemag.org/content/advances/suppl/2015/02/11/1.1.e1400005.DC1/1400005_SM.pdf%5Dsupplemental”>http://advances.sciencemag.org/content/advances/suppl/2015/02/11/1.1.e1400005.DC1/1400005_SM.pdf]supplemental materials/url give more insight into how the universities were selected; they chose schools with PhD programs that are ranked by U.S. News & World Report, so they were deliberately choosing doctoral-granting universities. (I’ll come back to this in a minute.)
Clauset, who is the first author of the science article and an author on the Slate article, is an expert in network science and data mining - his specialty is actually looking at large-scale patterns that emerge from large messy datasets. THe analysis method they used is sound (academics have actually been discussion this article for several months - it came out in February.)
This is no secret, and has long been known among academics. Although it is possible to get a tenure-track position from a less prestigious or lower-ranked university/PhD program, it is much, much easier to get one if you attend a well-reputed program. The better ranked your program is, the better chances you have. There are some lower-tier PhD programs that hardly place any PhD students into tenure-track positions at all. And then there are some top-tier programs (in every field) in which nearly every alumnus gets a tenure-track job or prestigious fellowship. It’s true across most disciplines - some disciplines, like nursing and accounting, feel it less because they have a faculty shortage, but it’s still true that an Emory-trained nursing PhD is more likely to end up at Emory or Penn than a East Carolina-trained nursing PhD.
And no, they didn’t look at smaller regional universities or LACs in the analysis - the study was limited to doctoral-degree granting universities since those are the ones ranked by U.S. News. But if you take a look at the faculty of these universities you’ll see the same patterns. The departments of elite LACs are dominated by PhDs from top programs. Mid-ranked LACs still mostly have faculty who graduated from top programs, with soem faculty from some mid-ranked programs sprinkled in. (@snarlatron actually provided a pretty good example; all 7 of those institutions are top U.S. institutions. I don’t know what field those faculty are in, but in my field 4 out of the 6 U.S. institutions are top 30 and the other 2 are in the top 75-100 of a field that has 250-300 PhD programs. The Canadian university, Guelph, is actually one of the top Canadian research universities).
Even smaller, less well-known LACs have more prestigious faculty than you’d expect. And this is especially if the school is located in a desirable metropolitan area. I checked out one small LAC in Atlanta I know of (Oglethorpe University) and their four-person department is represented by PhDs from Michigan, Georgia State, Emory and UW-Madison. UW and Michigan are both top 5 programs; Emory is around the top 50ish (and again, there are around 250-300 PhD programs in psychology) and Georgia State is top 75ish. I also applied for a public health position at College of Charleston, and was surprised that the faculty all had their PhDs from top public health institutions even though they had what looked like a 3/3 or 3/4 load.