Unemployment among US scientists and engineers is now at its lowest level since the early 1990s, according to figures released last month by the National Science Foundation (NSF). But the trends associated with the quality of those jobs, and the satisfaction of the people who fill them, are surprisingly hard to gauge.

Overall, the unemployment rate for scientists and engineers fell from 3.2% in 2003 to 2.5% in 2006. Generally, the higher the level of the degree, the lower the rate of unemployment — only 1.6% of those with doctorates were unemployed in 2006 compared with 2.9% of those with bachelor's degrees. Meanwhile, the total number of scientists and engineers — anyone with at least a bachelor's degree — grew by 4.5%, or roughly 1 million people.

But there are caveats. NSF statistics from January show that part-time positions in academia, which usually don't have work benefits, are on the rise. The number of people classified as non-faculty members — full and part-time adjunct faculty, lecturers, research associates, administrators and postdocs — rose by 85% to 76,600 between 1993 and 2006, whereas full-time faculty positions went up by only 15%. Indeed, in academia the proportion of science and engineering doctorate holders in full-time faculty employment fell from 88% in the early 1970s to 72% in 2006. And many full-time academic scientists, particularly biomedical researchers, are increasingly filling their days with grant writing rather than science thanks to tightened federal science budgets.

Meanwhile, more scientists and engineers are doing postdocs — 45% in 2006 compared with 41% in 1995, according to other NSF figures released last month. Roughly one-third said they took postdocs for 'additional training', but many, especially in the life sciences, often stay in those positions because they have few other job options in academia.

These figures provide only a glimpse of the issues surrounding job satisfaction. The quality, not just the quantity, of science and engineering jobs deserves further study.