For baseball pitchers, it’s the earned run average. For National Football League passers, it’s the quarterback rating. In each case, a single number gives some sense of a player’s value.

How would you quantify the cumulative impact and relevance of a researcher’s scientific work? Furthermore, is there a single number that would usefully characterize a scientist’s output?
“In a world of limited resources, such quantification (even if potentially distasteful) is often needed for evaluation and comparison purposes,” physicist Jorge E.