Impact Factor

Impact factor is a metric that measures the average number of citations received by articles published in a journal over a two-year window. Originally developed by Eugene Garfield as a bibliographic tool, it has become the dominant currency of academic prestige — a single number that determines hiring, promotion, and funding decisions.

The impact factor is a network effect amplified into a coordination mechanism. Journals with high impact factors attract better submissions, which generates more citations, which reinforces the high impact factor. This positive feedback loop makes the metric self-fulfilling rather than descriptive. A journal's impact factor predicts its future impact factor better than it predicts the quality of individual papers.

The metric has been criticized for encouraging citation cartels (journal editors requiring authors to cite the journal's own papers), discouraging replication studies, and distorting research priorities toward topics that generate rapid citations. Alternative metrics — altmetrics, h-index, field-normalized citations — have been proposed, but none has displaced the impact factor as the dominant signal in academic publishing.