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Table 5.

Regression results from the APC OA hurdle models for Natural Resources and Conservation, Physical and Mathematical Sciences, and Social and Behavioral Sciences, showing the count data component (APC OA articles > 0) and the zero count component (APC OA articles = 0)

	Nat. Res. & Conservation				Phys. & Math. Sci.				Soc. & Behav. Sci.
	β	Sig.	e^β	Std. Err.	β	Sig.	e^β	Std. Err.	β	Sig.	e^β	Std. Err.
	Positive Count Component				Positive Count Component				Positive Count Component
Gender is Male	0.031		1.031	0.036	0.069	**	1.072	0.022	0.138	***	1.147	0.032
Institution is Public	−0.035		0.966	0.045	−0.079	***	0.924	0.021	0.043		1.044	0.034
Institution is AAU Member	0.038		1.039	0.032	0.174	***	1.190	0.019	0.145	***	1.156	0.032
Years Since Degree	−0.005	**	0.995	0.002	−0.003	*	0.997	0.001	0.007	***	1.007	0.002
Professorial Rank	0.021		1.021	0.028	0.126	***	1.134	0.016	−0.157	***	0.855	0.028
Has Won Research Grants	0.177	***	1.193	0.032	0.225	***	1.253	0.018	0.374	***	1.453	0.034
Total Article Count	0.036	***	1.036	0.001	0.018	***	1.018	0.000	0.061	***	1.063	0.002
Log(θ)	0.967	***	2.631	0.054	−0.348	***	0.706	0.027	−0.653	***	0.521	0.063
Constant	0.653	***	1.921	0.070	0.368	***	1.446	0.040	−0.919	***	0.399	0.075
	Zero Hurdle Component				Zero Hurdle Component				Zero Hurdle Component
Gender is Male	−0.208		0.812	0.109	−0.011		0.989	0.037	0.044		1.045	0.030
Institution is Public	0.167		1.182	0.165	0.050		1.052	0.035	0.099	**	1.104	0.034
Institution is AAU Member	−0.079		0.924	0.106	0.016		1.016	0.032	0.185	***	1.203	0.031
Years Since Degree	−0.002		0.998	0.006	−0.010	***	0.990	0.002	0.003		1.003	0.002
Professorial Rank	−0.129		0.879	0.088	−0.008		0.992	0.027	−0.117	***	0.890	0.028
Has Won Research Grants	0.280	*	1.323	0.123	0.267	***	1.306	0.033	0.686	***	1.985	0.041
Total Article Count	0.254	***	1.289	0.011	0.177	***	1.194	0.003	0.141	***	1.152	0.002
Constant	−0.919	***	0.399	0.224	−0.953	***	0.385	0.060	−1.927	***	0.146	0.056
Observations	3,913				30,415				28,228
Log-likelihood	−8,287				−65,540				−32,000

	Nat. Res. & Conservation				Phys. & Math. Sci.				Soc. & Behav. Sci.
	β	Sig.	e^β	Std. Err.	β	Sig.	e^β	Std. Err.	β	Sig.	e^β	Std. Err.
	Positive Count Component				Positive Count Component				Positive Count Component
Gender is Male	0.031		1.031	0.036	0.069	**	1.072	0.022	0.138	***	1.147	0.032
Institution is Public	−0.035		0.966	0.045	−0.079	***	0.924	0.021	0.043		1.044	0.034
Institution is AAU Member	0.038		1.039	0.032	0.174	***	1.190	0.019	0.145	***	1.156	0.032
Years Since Degree	−0.005	**	0.995	0.002	−0.003	*	0.997	0.001	0.007	***	1.007	0.002
Professorial Rank	0.021		1.021	0.028	0.126	***	1.134	0.016	−0.157	***	0.855	0.028
Has Won Research Grants	0.177	***	1.193	0.032	0.225	***	1.253	0.018	0.374	***	1.453	0.034
Total Article Count	0.036	***	1.036	0.001	0.018	***	1.018	0.000	0.061	***	1.063	0.002
Log(θ)	0.967	***	2.631	0.054	−0.348	***	0.706	0.027	−0.653	***	0.521	0.063
Constant	0.653	***	1.921	0.070	0.368	***	1.446	0.040	−0.919	***	0.399	0.075
	Zero Hurdle Component				Zero Hurdle Component				Zero Hurdle Component
Gender is Male	−0.208		0.812	0.109	−0.011		0.989	0.037	0.044		1.045	0.030
Institution is Public	0.167		1.182	0.165	0.050		1.052	0.035	0.099	**	1.104	0.034
Institution is AAU Member	−0.079		0.924	0.106	0.016		1.016	0.032	0.185	***	1.203	0.031
Years Since Degree	−0.002		0.998	0.006	−0.010	***	0.990	0.002	0.003		1.003	0.002
Professorial Rank	−0.129		0.879	0.088	−0.008		0.992	0.027	−0.117	***	0.890	0.028
Has Won Research Grants	0.280	*	1.323	0.123	0.267	***	1.306	0.033	0.686	***	1.985	0.041
Total Article Count	0.254	***	1.289	0.011	0.177	***	1.194	0.003	0.141	***	1.152	0.002
Constant	−0.919	***	0.399	0.224	−0.953	***	0.385	0.060	−1.927	***	0.146	0.056
Observations	3,913				30,415				28,228
Log-likelihood	−8,287				−65,540				−32,000

* p < 0.05; ** p < 0.01; *** p < 0.001.

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