The teaching score: a new metric?

This article from the New York Times present the Open Syllabus Project

The Syllabus Explorer tool lets users search 1 million syllabi, used in the past 10 years, mostly in the US and English speaking countries, and presents a teaching score metric:

“Teaching Score’ (TS) is a numerical indicator of the frequency with which a particular work is taught. Overall Teaching Score is based on the rank of the text among citations in the total collection;”

Top 3 textbooks for Business:

Top 3 textbooks all fields combined: