Here’s a contribution to the discussion of citation rates in Astronomy (see this blog passim) by the estimable Paul Crowther who in addition to being an astronomer also maintains an important page about issues relating to STFC funding.
At last week’s Sheffield astrophysics group journal club I gave a talk on astronomical bibliometrics, motivated in part by Stuart Lowe’s H-R diagram of astronomers blog entry from last year, and the subsequent Seattle AAS 217 poster with Alberto Conti. These combined various versions of google search results with numbers of ADS publications. The original one was by far the most fun.
The poster also included Hirsch’s h-index for Americal Astronomical Society members, which is defined as the number of papers cited at least h times. Conti and Lowe presented the top ten of AAS members, with Donald Schneider in pole position, courtesy of SDSS. Kevin Pimblett has recently compiled the h-index for (domestic) members of the Astronomical Society of Australia, topped by Ken Freeman and Jeremy Mould.
Even though many rightly treat bibliometrics with distain, these studies naturally got me curious about comparable UK statistics. The last attempt to look into this was by Alex Blustin for Astronomy and Geophysics in 2007, but he (perhaps wisely) kept his results anonymous. For the talk I put together my attempt at an equivalent UK top ten, including those working overseas. Mindful of the fact that scientists could achieve a high h-index through heavily cited papers with many coauthors, I also looked into using normalised citations from ADS for an alternative, so-called hl,norm-index. I gather there are a myriad of such indices but stuck with just these two.
Still, I worried that my UK top ten would only be objective if I were to put together a ranked list of the h-index for every UK-based astronomy academic. In fact, given the various pros and cons of the raw and hl,norm-indexes, I thought it best to use an average of these scores when ranking individual astronomers.
For my sample I looked through the astrophysics group web pages for each UK institution represented at the Astronomy Forum, including academics and senior fellows, but excluding emeritus staff where apparent. I also tried to add cosmology, solar physics, planetary science and gravitational wave groups, producing a little over 500 in total. Refereed ADS citations were used to calculate the h-index and hl,norm-index for each academic, taking care to avoid citations to academics with the same surname and initial wherever possible. The results are presented in the chart.
Andy Fabian, George Efstathiou and Carlos Frenk occupy the top three spots for UK astronomy. Beyond these, and although no great football fan, I’d like to use a footballing analogy to rate other academics, with the top ten worthy of a hypothetical Champions League. Others within this illustrious group include John Peacock, Rob Kennicutt and Stephen Hawking.
If these few are the creme de la creme, I figured that others within the top 40 could be likened to Premier League teams, including our current RAS president Roger Davies, plus senior members of STFC committees and panels, including Andy Lawrence, Ian Smail and Andrew Liddle.
For the 60 or so others within the top 20 percent, I decided to continue the footballing analogy with reference to the Championship. At present these include Nial Tanvir, Matthew Bate, Steve Rawlings and Tom Marsh, although some will no doubt challenge for promotion to the Premier League in due course. The remainder of the top 40 per cent or so, forming the next two tiers, each again numbering about 60 academics, would then represent Leagues 1 and 2 – Divisons 3 and 4 from my youth – with Stephen Serjeant and Peter Coles, respectively, amongst their membership.
The majority of astronomers, starting close to the half-way point, represent my fantasy non-league teams, with many big names in the final third, in part due to a lower citation rate within certain sub-fields, notably solar and planetary studies. This week’s Times Higher Ed noted that molecular biology citation rates are 7 times higher than for mathematics, so comparisons across disciplines or sub-disciplines should be taken with a large pinch of salt.
It’s only the final 10 percent that could be thought of as Sunday League players. Still, many of these have a low h-index since they’re relatively young and so will rapidly progress through the leagues in due course, with some of the current star names dropping away once they retire. Others include those who have dedicated much of their careers to building high-impact instruments and so fall outside the mainstream criteria for jobbing astronomers.
This exercise isn’t intended to be taken too seriously by anyone, but finally to give a little international context i’ve carried out the same exercise for a few astronomers based outside the UK. Champions League players include Richard Ellis, Simon White, Jerry Ostriker, Michel Mayor and Reinhard Genzel, with Mike Dopita, Pierro Madau, Simon Lilly, Mario Livio and Rolf Kudritzki in the Premier League, so my ball-park league divisions seem to work out reasonably well beyond these shores.
Oh, I did include myself but am too modest to say which league I currently reside in…