Bias in the journal impact factor

TL;DR

This paper discusses how the journal impact factor (JIF) is biased due to sampling issues, favoring journals with rapid citation accrual, and suggests potential adjustments for more accurate impact measurement.

Contribution

It identifies biases in the JIF caused by sampling limitations and proposes that adjustments could improve its reliability as a measure of journal impact.

Findings

JIF sampling is biased towards rapid-impact journals.

Many journals show consistent citation patterns over years.

Adjustments to JIF could yield more accurate impact assessments.

Abstract

The ISI journal impact factor (JIF) is based on a sample that may represent half the whole-of-life citations to some journals, but a small fraction (<10%) of the citations accruing to other journals. This disproportionate sampling means that the JIF provides a misleading indication of the true impact of journals, biased in favour of journals that have a rapid rather than a prolonged impact. Many journals exhibit a consistent pattern of citation accrual from year to year, so it may be possible to adjust the JIF to provide a more reliable indication of a journal's impact.