Each text is assigned a count, registering the number of times it appears in syllabi, and a teaching score, “a numerical indicator of the frequency with which a particular work is taught,” according to the site. For instance, a search for “economics” shows Paul Krugman at the top of the list with his iconic “Economics,” which gets a count of 1,081 and score of 89.4. It doesn’t actually show up under economics texts either, as it is generally taught along with philosophy texts such as “The Social Contract,” by Jean-Jacques Rousseau; “Leviathan,” by Thomas Hobbes; and “On Liberty,” by John Stuart Mill.