  Since its creation in 1991, arXiv has become central to the diffusion of
research in a number of fields. Combining data from the entirety of arXiv and
the Web of Science (WoS), this paper investigates (a) the proportion of papers
across all disciplines that are on arXiv and the proportion of arXiv papers
that are in the WoS, (b) elapsed time between arXiv submission and journal
publication, and (c) the aging characteristics and scientific impact of arXiv
e-prints and their published version. It shows that the proportion of WoS
papers found on arXiv varies across the specialties of physics and mathematics,
and that only a few specialties make extensive use of the repository. Elapsed
time between arXiv submission and journal publication has shortened but remains
longer in mathematics than in physics. In physics, mathematics, as well as in
astronomy and astrophysics, arXiv versions are cited more promptly and decay
faster than WoS papers. The arXiv versions of papers - both published and
unpublished - have lower citation rates than published papers, although there
is almost no difference in the impact of the arXiv versions of both published
and unpublished papers.
