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Table 4. 
Regression results from the APC OA hurdle models for Engineering, Family, Consumer, and Human Sciences, Health Professions Sciences, and Humanities, showing the count data component (APC OA articles > 0) and the zero count component (APC OA articles = 0)
 EngineeringFam., Cons., & Hum. Sci.Health Professions Sci.Humanities
βSig.e^βStd. Err.βSig.e^βStd. Err.βSig.e^βStd. Err.βSig.e^βStd. Err.
  Positive Count Component Positive Count Component Positive Count Component Positive Count Component 
Gender is Male −0.005   0.995 0.021 0.073 * 1.076 0.035 0.277 *** 1.320 0.023 0.085   1.088 0.078 
Institution is Public −0.091 *** 0.913 0.019 −0.081   0.922 0.046 −0.077 ** 0.925 0.026 −0.086   0.918 0.083 
Institution is AAU Member 0.086 *** 1.090 0.017 0.085 * 1.088 0.036 0.212 *** 1.236 0.024 −0.088   0.916 0.081 
Years Since Degree −0.004 *** 0.996 0.001 0.003   1.003 0.002 −0.004 ** 0.996 0.001 0.011 * 1.012 0.005 
Professorial Rank 0.023   1.023 0.015 −0.073 * 0.929 0.032 0.019   1.019 0.020 −0.133   0.875 0.071 
Has Won Research Grants 0.237 *** 1.267 0.017 0.367 *** 1.443 0.040 0.173 *** 1.189 0.024 0.372 ** 1.451 0.121 
Total Article Count 0.029 *** 1.030 0.000 0.033 *** 1.034 0.001 0.030 *** 1.031 0.001 0.148 *** 1.160 0.011 
Log(θ) 0.546 *** 1.727 0.027 0.102   1.108 0.061 0.404 *** 1.497 0.035 −2.951 ** 0.052 1.010 
Constant 0.396 *** 1.486 0.036 0.060   1.061 0.074 0.364 *** 1.439 0.044 −3.872 *** 0.021 1.006 
  Zero Hurdle Component Zero Hurdle Component Zero Hurdle Component Zero Hurdle Component 
Gender is Male −0.149 ** 0.862 0.046 −0.089   0.915 0.047 0.603 *** 1.827 0.050 −0.018   0.982 0.040 
Institution is Public −0.079   0.924 0.042 0.061   1.063 0.062 0.206 *** 1.228 0.057 0.002   1.002 0.043 
Institution is AAU Member −0.086 * 0.917 0.036 0.220 *** 1.246 0.048 0.336 *** 1.399 0.051 0.228 *** 1.256 0.040 
Years Since Degree −0.008 *** 0.992 0.002 −0.005   0.995 0.003 0.000   1.000 0.003 −0.017 *** 0.983 0.002 
Professorial Rank −0.090 ** 0.914 0.032 −0.049   0.952 0.041 −0.034   0.967 0.040 0.099 ** 1.104 0.037 
Has Won Research Grants 0.469 *** 1.598 0.039 0.500 *** 1.649 0.081 0.395 *** 1.484 0.067 0.464 *** 1.591 0.077 
Total Article Count 0.164 *** 1.178 0.003 0.176 *** 1.193 0.004 0.179 *** 1.195 0.004 0.243 *** 1.276 0.005 
Constant −0.715 *** 0.489 0.071 −2.007 *** 0.134 0.088 −1.880 *** 0.153 0.079 −2.957 *** 0.052 0.076 
Observations 22,658       13,609       13,098       34,159       
Log-likelihood −42,670       −15,330       −24,050       −12,790       
 EngineeringFam., Cons., & Hum. Sci.Health Professions Sci.Humanities
βSig.e^βStd. Err.βSig.e^βStd. Err.βSig.e^βStd. Err.βSig.e^βStd. Err.
  Positive Count Component Positive Count Component Positive Count Component Positive Count Component 
Gender is Male −0.005   0.995 0.021 0.073 * 1.076 0.035 0.277 *** 1.320 0.023 0.085   1.088 0.078 
Institution is Public −0.091 *** 0.913 0.019 −0.081   0.922 0.046 −0.077 ** 0.925 0.026 −0.086   0.918 0.083 
Institution is AAU Member 0.086 *** 1.090 0.017 0.085 * 1.088 0.036 0.212 *** 1.236 0.024 −0.088   0.916 0.081 
Years Since Degree −0.004 *** 0.996 0.001 0.003   1.003 0.002 −0.004 ** 0.996 0.001 0.011 * 1.012 0.005 
Professorial Rank 0.023   1.023 0.015 −0.073 * 0.929 0.032 0.019   1.019 0.020 −0.133   0.875 0.071 
Has Won Research Grants 0.237 *** 1.267 0.017 0.367 *** 1.443 0.040 0.173 *** 1.189 0.024 0.372 ** 1.451 0.121 
Total Article Count 0.029 *** 1.030 0.000 0.033 *** 1.034 0.001 0.030 *** 1.031 0.001 0.148 *** 1.160 0.011 
Log(θ) 0.546 *** 1.727 0.027 0.102   1.108 0.061 0.404 *** 1.497 0.035 −2.951 ** 0.052 1.010 
Constant 0.396 *** 1.486 0.036 0.060   1.061 0.074 0.364 *** 1.439 0.044 −3.872 *** 0.021 1.006 
  Zero Hurdle Component Zero Hurdle Component Zero Hurdle Component Zero Hurdle Component 
Gender is Male −0.149 ** 0.862 0.046 −0.089   0.915 0.047 0.603 *** 1.827 0.050 −0.018   0.982 0.040 
Institution is Public −0.079   0.924 0.042 0.061   1.063 0.062 0.206 *** 1.228 0.057 0.002   1.002 0.043 
Institution is AAU Member −0.086 * 0.917 0.036 0.220 *** 1.246 0.048 0.336 *** 1.399 0.051 0.228 *** 1.256 0.040 
Years Since Degree −0.008 *** 0.992 0.002 −0.005   0.995 0.003 0.000   1.000 0.003 −0.017 *** 0.983 0.002 
Professorial Rank −0.090 ** 0.914 0.032 −0.049   0.952 0.041 −0.034   0.967 0.040 0.099 ** 1.104 0.037 
Has Won Research Grants 0.469 *** 1.598 0.039 0.500 *** 1.649 0.081 0.395 *** 1.484 0.067 0.464 *** 1.591 0.077 
Total Article Count 0.164 *** 1.178 0.003 0.176 *** 1.193 0.004 0.179 *** 1.195 0.004 0.243 *** 1.276 0.005 
Constant −0.715 *** 0.489 0.071 −2.007 *** 0.134 0.088 −1.880 *** 0.153 0.079 −2.957 *** 0.052 0.076 
Observations 22,658       13,609       13,098       34,159       
Log-likelihood −42,670       −15,330       −24,050       −12,790       

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

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