Why it matters when you are writing
The arithmetic is a mean over a distribution that is nothing like normal. A small number of articles collect most of the citations while the majority collect few, which means the average sits well above the typical paper. Judging an individual article by its venue’s impact factor is a statistical error before it is an ethical one, and it is the reason the DORA declaration asks assessors to stop doing it.
The number is also field-dependent in ways that make cross-disciplinary comparison meaningless. Molecular biology cites fast and cites recently; mathematics and much of the humanities cite slowly over decades, so their journals score low by construction. Comparing a mathematics journal’s factor to a cell biology journal’s says something about citation culture and nothing about quality.
It still shapes careers, and pretending otherwise is not useful. Hiring committees, funders, and some national assessment systems continue to use it, which is why researchers reasonably consider it when choosing where to submit. Consider it alongside the things that actually matter for your work: whether the readership is the one you need, how long review takes, and whether the article will be openly accessible to the people you want to reach.
