Calculated by an independent body, the Institute for Scientific Information, the impact of a journal is the number of times an average paper in that journal is cited elsewhere in a given year.

ECONOMIST: Peer review

Indeed, he predicts that for the average journal today, five extra years' worth of online availability will cause a precipitous drop in the number of articles receiving one or more citations from 600 to 200 a year.

ECONOMIST: Is the web narrowing scientists�� expertise?