The Number That's Devouring Science

The impact factor, once a simple way to rank scientific journals, has become an unyielding yardstick for hiring, tenure, and grants

In the beginning, during the late 1950s, it was just an innocent idea in Eugene Garfield's head. A Philadelphia researcher who described himself as a "documentation consultant," Mr. Garfield spent his free time thinking about scientific literature and how to mine information from it.

He eventually dreamed up something he called an "impact factor," essentially a grading system for journals, that could help him pick out the most important publications from the ranks of lesser titles. To