Key points are not available for this paper at this time.
The full text of this article is currently not available on the LRA (embargoed by publisher until October 2012). The published version is available from the publisher's website at: http://www.tandf.co.uk/journals/routledge/09585192.html ; DOI: 10.1080/09585192.2011.561967
Wood et al. (Fri,) studied this question.