Wide variations in the career prospects of postdoctoral researchers across disciplines suggest that two distinct research cultures continue to co-exist in universities.
In the physical and biological sciences, an army of postdoctoral workers is responsible for most of the research effort. Many are in research-only posts and part of large research groups; many will further their careers in industry; few will secure a permanent lectureship.
In the social sciences and the arts and humanities, on the other hand, scarcer research resources mean fewer research assistants. The chances of securing a permanent post in a university are much healthier. The vast majority of postdoctoral jobs involve teaching as well as research, and many young researchers are able to publish work on their own and prove their worth early on. Research assistantships are treated as the first step on the academic career ladder.
Peter Main, education and science director at the Institute of Physics, said that the large numbers of postdocs in subjects such as physics and chemistry meant a smaller percentage would win permanent contracts.
"Almost every research-intensive department has as many postdocs as staff, and you can't make the numbers balance," he said. Postdocs in physics will compete for possibly one academic appointment per year in a department.
Libby Steele, manager of professional education and development at the Royal Society of Chemistry, said: "For most chemistry postdocs, being a research assistant is a precursor for moving into industry."
Mr Main added that developing career structures for postdocs remain difficult. "Many in the arts and humanities use postdocs in a much more rounded role for teaching and research rather than just research. There's much less of an expectation among science postdocs that they will carry on to become lecturers," he said.
The Economic and Social Research Council, which is concerned about the recruitment of young academics in key disciplines such as economics, is undertaking a demographic study of its community - making comparisons with academics in the physical sciences. It revealed a far higher proportion of research-only posts as opposed to lectureships in the physical sciences.
There is also a higher proportion of staff aged under 35 in physics and chemistry than in social science disciplines.
A spokesperson for the council said variations in the chances of securing permanent jobs probably reflected the fact that more research in social science (and arts and humanities) is individual rather than team based.
"This means that it is more likely that people in these areas will be able to publish in their own right at an early stage in their careers."
Bill Brooks, education director at Southampton University and chairman of the Council of Deans of Arts and Humanities, said there appeared to be a trade-off between the availability of permanent contracts and the amount of money available for postdoctoral research.
Miriam David, professor of policy studies in education at the Institute of Education and acting chair of the Academy of Social Sciences, also highlighted the link between permanent contracts and a relative lack of research cash. "There are far fewer postdoctoral research positions in the social sciences and the tendency historically is that they would move on to a teaching contract," she said.
However, the job prospects for young scientists may improve in future, said Iain Cameron, head of Research Council UK's Research Careers and Diversity Unit. There was a wave of recruitment in the sciences in the 1970s and 1980s when a lot of new lectureships were created.
"There's a demographic bulge in the 60-65 bracket," Dr Cameron said. "Posts will become available in the next five years or so, but at the moment a lot of people are approaching retirement."
New European Union laws on fixed-term contracts, meanwhile, could transform the situation for hundreds of postdocs in July 2006. For the first time, those on contracts for more than four years will be automatically entitled to a permanent contract.
'I'm not the only one with a prestigious fellowship who can't get an academic post'
Postdoctoral researcher David McKee is finding it hard to secure a permanent post, even with a Natural Environment Research Council fellowship.
He is a fellow in the biomolecular and chemical physics research group in Strathclyde University's physics department.
The department has up to 40 researchers and 30 academics, so competition for permanent posts is fierce and the prospects are dismal.
"I can't get an interview in my own department for an academic post, never mind a job - and I'm not the only one who has either got or held prestigious fellowships but who can't get an academic post."
Dr McKee blames the research assessment exercise for making universities less keen on innovative research, such as the oceanographical optics research he is involved in.
"If you are doing off-mainstream research, they are not interested. With the RAE there's increased pressure to have big strong groups and financial pressure to perform well in the RAE. There are intellectual costs, and diversity is taking a hammering."
Dr McKee struggles with the word "career" with reference to academic research.
"This has connotations of structure, which, frankly, academe doesn't have," he said.
He held a number of temporary contracts before getting the fellowship and he puts the variation in chances of securing a permanent job by subject area down to the number of people involved.
"Physics departments are highly research-focused. The number of people employed as researchers is probably higher than in arts departments, so there is more competition for permanent posts," he said.