Research indicates that selectivity in staffing is positively related to firm performance, according to an article in the Acad. of Mgt. Rev., 1996 Aug., at 952. Perhaps there lurks in that finding a comparative metric for law departments.
If we had data from a number of law departments as to how long it took them to fill open positions over several years and how many applicants they interviewed, we might discover that the more discriminating departments have better benchmark ratios, such as lawyers per billion. If you are very picky and careful about whom you select, it is more likely that your talent is better, fits your needs more precisely, and performs more effectively.