Is lab productivity systematically too low to get students and postdocs jobs?

Science has a “Careers” section, and a few weeks ago they published an article titled, “Staffing labs for optimal productivity”. The article discusses the results of social science research by Annamaria Conti and Christopher Liu, who investigated the research output of biology labs at MIT from 1966 to 2000. The records included the composition of each lab, with the number of graduate students and postdocs, with funding sources, and the output in terms of journal articles. Here’s a paragraph with a nutshell version of the study’s results:

Using regression analysis, the authors found that the bigger labs in their dataset were more productive in terms of the overall number of papers published per year. For the average-sized laboratory in the study—roughly five postdocs, three graduate students, and two technicians—adding one lab member was correlated with an extra quarter publication. As lab size increased, productivity continued to go up but at a slower and slower rate. Once the lab size reached 25, adding new people was counterproductive.

When I looked into those numbers, I have to say I was shocked at how little productivity came from adding lab members.

Not all new employees were found to have the same impact, however. An extra postdoc in an average-sized lab added 0.31 publications, whereas an extra graduate student meant only an extra 0.14 (bearing in mind that these are suggestive correlations with no clear implication of cause and effect). Among postdocs, postdoctoral fellows—those with actual fellowships—added more productivity than grant-supported postdocs did (0.29 versus 0.19). Extra technicians, the authors found, did not correlate with extra publications.

So hiring a postdoc enabled a lab (on average) to publish one additional paper over three years. The average lab published a bit more than five articles per year and had ten members including the principal investigator, 4.5 of whom were postdocs, 3.3 graduate students and 1.5 technicians.

What shocked me is that this level of productivity, while quite reasonable across an entire lab, is low for the trainees. Today, strong candidates for tenure-track assistant professor positions tend to have more than one first-authored publication per year over the last year or two. The best candidates often have two or three per year. Of course, that’s today, and this series of records goes back into the 1970s when jobs required fewer publications. Still, when we look at the lab productivity, a mean of five publications split between 4.5 postdocs, with additional postdocs only adding 0.3 publications per year, is not going to yield a very good publication record for the modal postdoc. Especially when a few high achievers were no doubt racking up two or more publications out of that total, or the principal investigator had a first-author publication herself.

When I plan budgets, I try to calibrate my projected research outputs to the number of publications that will realistically help trainees on the job market. For a small lab in biological anthropology, that’s allowing two publications per postdoc annually, and one first-authored publication annually for a PhD candidate. I think both these are conservatively low, but I have had reviewers tell me that is an unrealistic level of publication. I think its irresponsible to plan a lower amount, in my field: If my budget includes salary or support for these trainees, my project should give them appropriate opportunities for career advancement. Some may choose to pursue different career options than tenure-track, but that doesn’t lessen my responsibility to provide them adequate opportunities.

Many others have pointed out ways that the system of laboratory science is built around disposable trainee labor. This study was directed toward the study of productivity in different sizes of labs, and not toward career outcomes for the postdocs and graduate students. It would be useful to see whether labs with higher publications per trainee also had higher placement rates for their trainees.


Conti A, Liu CC. 2015. Bringing the lab back in: Personnel composition and scientific output at the MIT Department of Biology. Research Policy (online) doi:10.1016/j.respol.2015.01.001