How can impact factors be improved?

Impact factors are widely used to rank and evaluate journals. They are also often used inappropriately as surrogates in evaluation exercises. The inventor of the Science Citation Index warns against the indiscriminate use of these data. Fourteen year cumulative impact data for 10 leading medical journals provide a quantitative indicator of their long term influence. In the final analysis, impact simply reflects the ability of journals and editors to attract the best papers available.