Self-archiving and citation impact during an embargo period

Alma Swan, Author compliance with publisher open access embargoes: a study of the journal Nature Physics, Technical Report, School of Electronics & Computer Science, University of Southampton, 2007.  Self-archived April 25, 2007.  Excerpt: 

...In October 2005, the NPG [Nature Publishing Group] launched a new journal called Nature Physics.…[I wanted to know]...how physicists who...work in the sub-disciplines that habitually self-archive in the arXiv would respond to the NPG's [new] 6-month embargo period.…

As soon as the first issue of Nature Physics was published and it was possible to see the table of contents I carried out...a webwide search for the articles published in that first issue. I searched for the papers classified as Letters (because in Nature these are actually primary research papers) and Articles (longer research papers) only.…

I looked for [both] postprints...and preprints.…

The results are as follows, for Day One after publication.

Letters to Nature Physics (6 in total):

• 2 had the postprint version in arXiv
• 2 had the preprint version in arXiv...
• 2 were not in arXiv, though one of these appeared as the publisher's PDF on the author's home page.…

Articles (2 in total):

• both had postprints in arXiv

In total, then, only one article out of 8 was not freely available on the web somewhere immediately upon publication.…

In addition, the four postprints in arXiv had gathered a total of nine citations and 44 downloads by the time they appeared in the journal.