| Abstract: |
Aggregate citation behavior plays a key role in scientific knowledge
diffusion, as citations document the collective and cumulative nature of
knowledge production. Additionally, citations are commonly taken as input for
several influential evaluative metrics used to assess researchers’
performance. Nevertheless, little effort has been devoted to understanding and
quantifying how article citations evolve over the years following an article’s
publication and how these trends vary across fields of research. By collecting
and analyzing a dataset consisting of more than five million citations to
59,707 research articles from 12 dissimilar fields of research, we quantify
how citations evolve across fields of research as articles grow older.
Analyzing raw citation data spanning different periods poses several
methodological challenges; to tackle them, we employ quantile regression, a
technique that makes it possible to control for citation inflation (the fact
that citations have become more common nowadays) and to take into
consideration the well-known asymmetry in the distribution of citations. We
find that citations follow a life-cycle pattern. In the first years after
publication, articles generally receive a small but growing number of
citations until, eventually, they reach a peak from which they then decline.
Importantly, the shape of these life cycles varies greatly from one field to
the next. Given that several influential metrics restrict their input to a
certain range in terms of the number of years since publication, these
differences are by no means neutral and should be taken into account when
evaluating researchers or their institutions. |