Macroevaluation
		¡ Axiom l The more a book in a library is exposed, the more effective the library. ¡ Defining “an exposure” as a simple count l Pros ¡ Easy; can different levels of granularity l Cons ¡ 5 × 1 day borrowing is five times more exposure than 1 × 5 day borrowing ¡ __________________________