Research: Decoupling of the minority PhD talent pool and assistant professor hiring in medical school basic science departments in the US

National Institute of General Medical Sciences, United States
Association of American Medical Colleges, United States
The George Washington University, United States

Nov 17, 2016

https://doi.org/10.7554/eLife.21393

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5 figures, 2 tables and 1 additional file

Figures

Figure 1

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Temporal trends in the populations of biomedical Underrepresented Minority (URM) and Well-Represented (WR) PhD graduates and assistant professors, 1980-2014.

Line charts showing the (i) annual population, (ii) population growth relative to 1980, and (iii) percentage representation of PhD graduates and assistant professors in basic science departments in medical schools for scientists from (A) URM and (B) WR racial-ethnic backgrounds. Data on the populations of PhD graduates and assistant professors in medical school basic science departments were obtained from the National Science Foundation Survey of Earned Doctorates (as compiled by Federation of American Societies for Experimental Biology), and the AAMC Faculty Roster, respectively (please see methods section for more information). Grey lines represent PhD graduates, and black lines represent assistant professors. In panels Aiii and Biii, solid grey lines represent the percentages of URM and WR PhD graduates among all students who receive PhDs in the U.S. (U.S. citizen, permanent resident, and international), and dotted lines show percentages among PhD graduates who are U.S. citizens and permanent residents. The relative growth of PhD graduates from URM backgrounds to assistant professors is greater than the same comparison among scientists from WR backgrounds (i.e., there was a significant interaction between the URM status and position, β=1.60; p=3.6*10⁻⁷; panels Aii and Bii). Data are available in Figure 1—source data 1.

https://doi.org/10.7554/eLife.21393.002

Figure 1—source data 1 PhD graduates and assistant professors (Total, URM and WR): 1980-2014.: https://doi.org/10.7554/eLife.21393.003
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Figure 2 with 1 supplement

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Candidate pool size, hiring and utilization of URM and WR assistant professors in basic biomedical science departments.

Scatter plots showing the (i) pool of potential candidates for assistant professor positions, (ii) annual number of assistant professors hired, and (iii) percentage of the potential candidate pool hired annually for scientists from (A) URM and (B) WR backgrounds. R² values in panels Aii and Bii are derived from correlating number of URM or WR assistant professors hired with the size of their respective pool of potential candidates. β in panels Aiii and Biii reflect the yearly percentage change in the fraction of the pools of URM and WR scientists hired into assistant professor positions. Asterisks represent significant values (p<10⁻⁴). Data are available in Figure 2—source data 1 and 2.

https://doi.org/10.7554/eLife.21393.004

Figure 2—source data 1 Assistant professor hiring and leaving (total, URM and WR): 1980-2014.: https://doi.org/10.7554/eLife.21393.005
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Figure 2—source data 2 Candidate pool and fraction hired (URM and WR): 1980-2014.: https://doi.org/10.7554/eLife.21393.006
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Figure 2—figure supplement 1

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Candidate pool size, hiring and utilization of URM and WR assistant professors in basic biomedical science departments: by gender.

Scatter plots showing the (i) pool of potential candidates for assistant professor positions, (ii) annual number of assistant professors hired, and (iii) percentage of the potential candidate pool hired annually for (A) URM Men, (B) URM Women, (C) WR Men, and (D) WR women. R² values in panels A-Dii were derived from correlating number of URM or WR assistant professors hired with the size of their respective pool of potential candidates. β in panels A-Diii reflect the yearly percentage change in the fraction of the pools of URM and WR scientists hired into assistant professor positions. Asterisks represent significant values (p<10⁻⁴). Data are available in Figure 2—source data 1 and 2.

https://doi.org/10.7554/eLife.21393.007

Figure 3

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System dynamics model of assistant professor hiring.

(A) A traditional “pipeline” view of faculty hiring. A fraction of the total stock of PhD graduates pursues faculty positions, and thus become candidates on the market. Candidates on the market are composed primarily of the subset of postdoctoral scientists pursuing faculty careers in medical school basic science departments but can include those who have non-traditional career paths such as the rare PhD student who proceeds directly to the faculty job market. Each year, candidates on the market are hired into the stock of assistant professors at a rate equal to the total number of slots available (“slots available”), and candidates who are not hired remain in the pool conditional on hiring probability (“market dropout”). After six years, assistant professors leave the system (either via promotion or contract termination, “Assistant Professor Tenure or Leave”). Boxes represent stocks (quantities), hourglasses represent flows (rates; writing italicized), variables are bolded, blue arrows represent causal connections between factors, and clouds represent system boundaries (B) Intermediate conceptual model. The pool of PhD graduates is separated into two groups: those who will pursue and enter faculty positions in research-intensive environments (“Faculty Aspire”), and those who will pursue other career interests (“Other Aspire”). All “Faculty Aspire” graduates enter the academic job market (“Candidates on the Market”) and remain based on hiring probability, while the “Other Aspire” scientists depart the system. As the total number of PhD graduates grows (“Baseline PhD Graduate Growth Rate”), the populations of “Faculty Aspire” and “Other Aspire” graduates are expected to grow equally (i.e. they maintain the same, fixed proportions with respect to one another). Initial populations (P₀) of “Faculty Aspire” and “Other Aspire” candidates represent scaling factors that, together with the baseline growth rate, produce the number of PhD graduates in each stock. Candidates on the market are hired into the stock of assistant professors at a rate equal to the total number of slots available, and then depart the system six years later. (C) Elaborated model of faculty hiring for PhD scientists from WR and URM backgrounds with intervention to enhance workforce diversity. The career pathways of URM and WR scientists are conceptualized as independent, but are linked with respect to assistant professor hiring by the number of assistant professor slots available. URM and WR candidates are hired based on the number of slots available, and in proportion to their representation on the market (hence the influence of WR candidates on the URM hiring rate and vice versa). That is, the model posits no bias in hiring. In addition to baseline growth, the variable “URM Target Growth Rate” represents efforts from the scientific community to enhance workforce diversity. These additional URM scientists are initially added to the “URM other aspire” stock. The “transition rate” represents the percentage of URM other aspire scientists that enter the faculty market. As this rate increases, more URM candidates enter the academic job market. Candidates hired leave the system after six years, and the initial populations (P₀) are derived from empirical data as described in methods.

https://doi.org/10.7554/eLife.21393.008

Figure 4

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Model simulation: 1980-2013.

Scatter plots showing the performance of the model (open circles) compared to input data (filled circles) for the populations of (i) PhD graduates, (ii) assistant professors, and (iii) newly hired assistant professors for the (A) overall pool, (B) pool of URM scientists, and (C) pool of WR scientists. All R² values are significant at the p<0.0001 level.

https://doi.org/10.7554/eLife.21393.009

Figure 5

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Model predictions of URM assistant professor attainment.

Line graph showing model predictions for the percentage of URM PhD graduates (grey), and the corresponding percentages of URM assistant professors (black) as a function of various intervention strategies to increase faculty diversity in (A) short-term, through 2030, and (B) long-term, through 2080. All model runs assume an exponential increase in the number of PhDs from URM backgrounds. Thus, in all runs, the percentage of PhD scientists from URM backgrounds is 13.8% in 2030 and 73% in 2080. Simulations: (i) No change in transition rate (0.25%) or number of assistant professor positions. (ii) No change in transition rate (0.25%), increase the number of assistant professor positions by 100 per year, beginning in 2015. (iii) Increase transition rate to 10%, and no change in the number of assistant professor positions. (iv) Increase transition rate to 10% and increase the number of assistant professor positions by 100 per year, beginning in 2015.

https://doi.org/10.7554/eLife.21393.010

Figure 5—source data 1 Model predictions: percentage URM assistant professors by transition rate: 1980-2080 (current number of assistant professor positions): https://doi.org/10.7554/eLife.21393.011
Download elife-21393-fig5-data1-v2.xlsx
Figure 5—source data 2 Model predictions: percentage URM assistant professors by transition rate: 1980-2080 (100 new assistant professor positions, annually, beginning in 2015): https://doi.org/10.7554/eLife.21393.012
Download elife-21393-fig5-data2-v2.xlsx

Tables

Appendix 1—table 1

Model formulation.

https://doi.org/10.7554/eLife.21393.014

Notation	Description	Formulation
UTG	URM Target Growth Rate	$exp (t * C_{U T G})$
GR_WR,Other	WR Non-Faculty Student Growth Rate	BSG * P_0,WR,Other
GR_WR,Faculty	WR Faculty Student Growth Rate	BSG * P_0,WR,Faculty
GR_URM,Other	URM Non-Faculty Student Growth Rate	BSG * P_0,URM,Other
GR_URM,Faculty	URM Faculty Student Growth Rate	MAX(BSG * P_{0,URM,Faculty}, UTG * P_{0,URM,Faculty})
PHD_WR,Other	WR Non-Faculty PHD Graduates	PHD_WR,Other,0 $+ \int^{} G R_{W R, O t h e r} - D R_{W R, O t h e r} d t$
PHD_WR,Faculty	WR Faculty Student PHD Graduates	PHD_WR,Faculty,0 $+ \int^{} G R_{W R, F a c u l t y} - M R_{W R, F a c u l t y} d t$
PHD_URM,Other	URM Non-Faculty PHD Graduates	PHD_URM,Other,0 $+ \int^{} G R_{U R M, O t h e r} - D R_{U R M, O t h e r} d t$
PHD_URM,Faculty	URM Faculty PHD Graduates	PHD_{URM,Faculty,0} $+ \int^{} G R_{U R M, F a c u l t y} - M R_{U R M, F a c u l t y} - T R_{U R M, F a c u l t y} d t$
DR_WR,Other	WR Non-Faculty Student Departure Rate	PHD_WR.Other
MR_WR,Faculty	WR Faculty Student Market Entrance Rate	PHD_WR.Faculty
DR_URM,Other	WR Non-Faculty Student Market Entrance Rate	PHD_WR.Other
MR_URM,Faculty	WR Faculty Student Market Transition Rate	C_UTR*PHD_URM.Faculty
TR_URM,Faculty	WR Faculty Student Departure Rate	(1-C_UTR)*PHD_URM.Faculty
PD_WR	WR Candidates on the Market (e.g., Postdocs)	PD_{WR, 0} $+ \int^{} M R_{W R, F a c u l t y} - H R_{W R} - D R_{W R, F a c u l t y} d t$
PD_URM	URM Candidates on the Market (e.g., Postdocs)	PD_URM,0 $+ \int^{} M R_{U R M, F a c u l t y} - H R_{U R M} - D R_{U R M, F a c u l t y} d t$
π_URM	Proportion of URM candidates on the market	PD_URM/(PD_URM+ PD_WR)
HR_WR	Hiring rate of WR candidates	MIN[PD_WR,S*(1- π_URM)]
HR_URM	Hiring rate of URM candidates	MIN(PD_URM,S*π_URM)
DR_WR,Faculty	WR Faculty Student Departure Rate	${\begin{matrix} 0 & i f H R_{W R} < \frac{P D_{W R}}{5} \\ \frac{P D_{W R}}{5} & o t h e r w i s e \end{matrix}$
DR_URM,Faculty	URM Faculty Student Departure Rate	${\begin{matrix} 0 & i f H R_{U R M} < \frac{P D_{U R M}}{5} \\ \frac{P D_{U R M}}{5} & o t h e r w i s e \end{matrix}$
AP_WR	WR Assistant Professors	AP_{WR, 0} $+ \int^{} H R_{W R} - H R_{W R, t - 6} d t$
AP_URM	URM Assistant Professors	AP_URM,0 $+ \int^{} H R_{U R M} - H R_{U R M, t - 6} d t$

Note: $H R_{., t - 6}$ denotes hiring rate of assistant professors delayed by six time steps (i.e., the length of a tenure cycle). For timesteps <7, $H R_{., t - 6}$ is calculated by amortization of the initial value of assistant professors AP_{., 0}.

Appendix 1—table 2

Parameters and exogenous variables.

https://doi.org/10.7554/eLife.21393.015

Notation	Description	Value	Source
P_{0,URM,Faculty}	URM Faculty Student Growth Rate Multiplier	34.44	AAMC Faculty Roster (Imputed values, URM hiring 1980-1997)
P_0,URM,Other	URM Non-Faculty Student Growth Rate Multiplier	64	AAMC Faculty Roster (Exponential fit of URM PhD graduate growth and imputed URM hiring 1980-1997)
P_0,WR,Faculty	WR Faculty Student Growth Rate Multiplier	566.67	AAMC Faculty Roster (Imputed values, WR hiring 1980-1997)
P_0,WR,Other	WR Non-Faculty Student Growth Rate Multiplier	3500	AAMC Faculty Roster (Linear fit of WR PhD graduate growth and imputed WR hiring 1980-1997)
C_UTG	URM Target Growth Constant	0.0728	FASEB (Author estimation based on exponential fit to URM PhD graduation rate 1980-2013)
PHD_WR,Other,0	Initial WR Non-Faculty PhD Graduates	3570	FASEB (Author estimation based on number of WR PhD graduates)
PHD_WR,Other,0	Initial WR Faculty PhD Graduates	438	FASEB (Author estimation based on number of WR PhD graduates)
PHD_WR,Other,0	Initial URM Non-Faculty PhD Graduates	84.6	FASEB (Author estimation based on number of URM PhD graduates)
PHD_WR,Other,0	Initial URM Faculty PhD Graduates	25.4	FASEB (Author estimation based on number of URM PhD graduates)
C_UTR	URM Transition Rate Constant	0.0025	AAMC Faculty Roster (Author estimation based on % URM Assistant Professor 2014)
PD_{WR, 0}	Initial WR Candidates on the Market	511	AAMC Faculty Roster (Imputed Hiring Value)
PD_URM,0	Initial URM Candidates on the Market	19	AAMC Faculty Roster (Imputed Hiring Value)
S	Faculty Slots Available per Year	Step function time series: $S = {\begin{matrix} 601.11 \\ 1063.67 \end{matrix} \begin{matrix} t \in [0, 18) \\ t > 18 \end{matrix}}$	AAMC Faculty Roster (average of imputed hiring values: 1980-1997; 1998-2013)
AP_{WR, 0}	Initial WR Assistant Professors	3246	AAMC Faculty Roster
AP_URM,0	Initial URM Assistant Professors	132	AAMC Faculty Roster

Additional files

Source code 1 Vensim file containing the final system dynamics model of assistant professor hiring in basic science departments of medical schools.: https://doi.org/10.7554/eLife.21393.013
Download elife-21393-code1-v2.mdl