Are there too many science PhDs or too few jobs?

R0 is a term used by demographers and epidemiologists. In demographics it is the reproductive rate – the number of baby girls a newly born baby girl can be expected to have in her lifetime, so R0=1 means she is likely to have one child and replace herself. The authors of the study have used it as the mean number of new PhD’s that a typical tenure-track faculty member will graduate during his or her academic career. If they supervise one PhD student that graduate can replace the professor. If the number is higher than one, the number of positions must increase to accommodate the new graduates

A study by MIT researchers makes bleak reading for young scientists – at least if they want a job in a university. It says that the supply of science PhD graduates far outstrips available positions for them in academia in the US and the situation is only going to get worse.

"The system in many places is saturated, far beyond capacity to absorb new PhDs in academia at the rates that they are being produced," the report says.

But the solution is not in creating more tenured academic positions, it says, but focusing more on undergraduate and masters' level graduates to address the paradoxical shortage of suitable Science, Technology, Engineering and Mathematics (STEM) candidates demanded by American businesses.

Fewer than 17% of science, engineering and health-related PhD graduates find tenure-track positions within three years.

The authors, engineers Richard C. Larson, Navid Ghaffarzadegan, and Yi Xue, treat the problem as similar to a demographic one.

"We show that the reproduction rate in academia is very high," they write. "For example, in engineering, a professor in the US graduates 7.8 new PhDs during his/her whole career on average, and only one of these graduates can replace the professor’s position.

"This implies that in a steady state, only 12.8% of PhD graduates can attain academic positions in the USA."

A lack of growth on the demand side suggests that is unlikely to improve, the report says.

"Except computer science, which experienced rapid growth in the past 30 years, and life sciences with the average growth of 1.5% per year, many fields have seen little increase in their faculty slots."

But, in any case, increasing positions would only make things worse in the long-run, the authors say.

In demography, any living population eventually meets a ceiling of limited resources. Similarly in academia, the growing PhD population will eventually hit the natural ceiling of limited tenure-track positions. In some fields, it already has hit that limit. The physics of the system requires that the oversupply must move to non-academic positions or be underemployed in careers that require lesser degrees. Simply increasing the number of faculty slots will not solve the problem. More openings will increase the numbers of professors, and given their high ‘birth rates,’ the number of future PhD graduates. It is a positive feedback loop.

Ironically, American employers are crying out for suitable STEM candidates for jobs, for which the authors have the following solution:

Our analysis has shown that there are more STEM PhDs than the academic market can absorb, while the number of young people with lesser STEM credentials falls significantly short of market demand. At the education enterprise level, more focus on undergraduate and Masters’ level graduates can help ameliorate the STEM workforce supply–demand imbalance.

They describe the conundrum as "an engineering design puzzle" – how to design the academic research enterprise so as to perform the research effectively while at the same time reducing the ‘PhD birth rate’ of professors.

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