My post on the strange data underlying the new impact factor for eLife was read by many people. Thanks for the interest and for the comments and discussion that followed. I thought I should follow up on some of the issues raised in the post.
- eLife received a 2013 Impact Factor despite only publishing 27 papers in the last three months of the census window. Other journals, such as Biology Open did not.
- There were spurious miscites to papers before eLife published any papers. I wondered whether this resulted in an early impact factor.
- The Web of Knowledge database has citations from articles in the past referring to future articles!
1. Why did eLife get an early Impact Factor? It turns out that there is something called a partial Impact Factor. This is where an early Impact Factor is awarded to some journals in special cases. This is described here in a post at Scholarly Kitchen. Cell Reports also got an early Impact Factor and Nature Methods got one a few years ago (thanks to Daniel Evanko for tweeting about Nature Methods’ partial Impact Factor). The explanation is that if a journal is publishing papers that are attracting large numbers of citations it gets fast-tracked for an Impact Factor.
2. In a comment, Rafael Santos pointed out that the miscites were “from a 2013 eLife paper to an inexistent 2010 eLife paper, and another miscite from a 2013 PLoS Computational Biology paper to an inexistent 2011 eLife paper”. The post at Scholarly Kitchen confirms that citations are not double-checked or cleaned up at all by Thomson-Reuters. It occurred to me that journals looking to game their Impact Factor could alter the year for citations to papers in their own journal in order to inflate their Impact Factor. But no serious journal would do that – or would they?
3. This is still unexplained. If anybody has any ideas (other than time travel) please leave a comment.