Following up the links on a post by Eszter at Crooked Timber, I discovered that she shares with me an Erdös number of 3 (Eszter via Aronov and O’Rourke, mine via Fishburn and Wakker). This is pretty good for social science academics.
We thought this was worth a CT post, and came up with another issue. Although Movable Type and other systems encourage group blogging, they don’t, it seems, allow for jointly authored posts. This is of particular interest since it’s at least arguable that a joint post would count as co-authorship for Erdös number purposes (this comes back to the question, frequently discussed on this blog, of whether and how blog contributions should be listed on vitas). But more generally, it would seem as if joint posts would be worthwhile for at least some purposes.
The Erdos number site asserts that numbers as high as 15 have been found, but that, at least for mathematicians nearly all finite Erdös numbers are below 8. This seems about right, though mean, median and modal numbers must grow as those with low numbers die or retire, becoming unavailable for collaboration.