PNAS paper on the rise of the temporary workforce in science; average science career now lasts only five years!

Back in 1997, Alan Hale (of the Hale-Bopp comet) discussed problems of lack of opportunity in science, which issues were later discussed
on IPBiz:



IPBiz notes that there is a far more insidious internal brain drain: the waste of trained American minds. One recalls the letter of Alan Hale of Hale-Bopp fame, from the year 1997:

I am Alan Hale, the co-discoverer of Comet Hale-Bopp which, as I'm sure you're aware, is getting a tremendous amount of media attention at this time. Like I'm sure is true for many of you, I was inspired by the scientific discoveries and events taking place during my childhood to pursue a career in science only to find, after completing the rigors of undergraduate and graduate school, that the opportunities for us to have a career in science are limited at best and are which I usually describe as "abysmal." Based upon my own experiences, and those of you with whom I have discussed this issue, my personal feeling is that, unless there are some pretty drastic changes in the way that our society approaches science and treats those of us who have devoted our lives to making some of our own contributions, there is no way that I can, with a clear conscience, encourage present-day students to pursue a career in science. It really pains me a great deal to say something like that, but I feel so strongly about this that I have publicly made this statement at almost every opportunity I have been given.

I am trying to use the media attention that is currently being focused upon me to raise awareness of this state of affairs, and perhaps start to effect those changes that will allow me to convey a more positive message to the next generation. So far, I'm sensing a certain reluctance among the media to discuss this issue, as they seem far more interested in items which I consider to be irrelevant and unimportant. (...)



Flash forward more than twenty years, and note the appearance of a paper in PNAS on 11 December 2018 titled
Changing demographics of scientific careers: The rise of the temporary workforce by
Staša Milojević, Filippo Radicchi, and John P. Walsh, PNAS December 11, 2018 115 (50) 12616-12623; published ahead of print December 11, 2018.

The abstract states:



Contemporary science has been characterized by an exponential growth in publications and a rise of team science. At the same time, there has been an increase in the number of awarded PhD degrees, which has not been accompanied by a similar expansion in the number of academic positions. In such a competitive environment, an important measure of academic success is the ability to maintain a long active career in science. In this paper, we study workforce trends in three scientific disciplines over half a century. We find dramatic shortening of careers of scientists across all three disciplines. The time over which half of the cohort has left the field has shortened from 35 y in the 1960s to only 5 y in the 2010s. In addition, we find a rapid rise (from 25 to 60% since the 1960s) of a group of scientists who spend their entire career only as supporting authors without having led a publication. Altogether, the fraction of entering researchers who achieve full careers has diminished, while the class of temporary scientists has escalated. We provide an interpretation of our empirical results in terms of a survival model from which we infer potential factors of success in scientific career survivability. Cohort attrition can be successfully modeled by a relatively simple hazard probability function. Although we find statistically significant trends between survivability and an author’s early productivity, neither productivity nor the citation impact of early work or the level of initial collaboration can serve as a reliable predictor of ultimate survivability.

(emphasis added by IPBiz)

The matter of citations arises in the PNAS paper:



There is an abundance of studies that focus on the criteria that may affect researchers’ success in terms of the impact of their work, especially in terms of citations to publications. However, another, and perhaps more fundamental, aspect of success is the ability to perform research over the full extent of someone’s career, rather than leaving the field prematurely.



The concept of a "transient" is mentioned:


The minimal level of contribution to scientific knowledge is the production of a single paper. The existence of such authors was first pointed to by Price and Gürsey in 1976 (35), who named this type of author “transients” and established that they accounted for 25% of the population of scientists in the late 1960s. In Fig. 3, we find that the fraction of transients has remained relatively constant in most cohorts, although this category of authors has started to increase in recent cohorts across all three fields (since about the 1990s), especially in robotics and ecology. Notably, we also find that, unlike the fraction of lead authors, which is universal, the number of transients is field-dependent, with levels in astronomy similar to the ones Price and Gürsey (35) found and much higher rates (50–70%) in ecology and robotics. Interestingly, one-quarter of recent transients in all three fields were lead authors. This fraction was as high as one-half in the 1960s. This suggests that the threshold for lead authorship is often crossed even in the population that never genuinely embarks on a research path in that discipline.



This leads to "survival" analysis:


For authors who persist after the initial publication, we employ survival analysis to study their scientific career longevity. In Fig. 4, we show the survival curves of select cohorts spanning the period of the most recent four decades. Survival curves are calculated as the fraction of a cohort remaining after x years. While the survival curves of contemporaneous cohorts in different fields have different slopes, we see that the curves undergo a similar evolution in each field: from relatively long survival times in the 1980s to very rapid attrition of the scientific workforce in most recent times. We observe that until the 1980s (1990s for astronomy), more than half of each cohort had “full” (20+ y) careers. However, in recent decades, this is no longer the case. The results correspond to a continuous decline in the expected career length.



link to PNAS paperL https://www.pnas.org/content/115/50/12616

As to the words "temporary workforce" in the title of the PNAS paper, one recalls the long-ago work by William Bridges.
In a review of his JobShift book, one finds the text


The concept of secure employment is fading; being replaced by an “on demand” workforce hired
in on a temporary basis to meet market challenges.





See IPBiz post The "new normal" in jobs predicted long ago by William Bridges

The 1994 book by Bridges: Jobshift: How To Prosper In A Workplace Without Jobs

**Thus, the 1994 book by Bridges and the 1997 communication by Hale (among others) fairly anticipated the analysis of
the 2018 PNAS paper.