Table 3.
Results of random-effects negative binomial panel regressions with main and interaction effects.
| Model 1 |
Model 2 |
Model 3 |
Model 4 |
|||||
|---|---|---|---|---|---|---|---|---|
| EC | SE | EC | SE | EC | SE | EC | SE | |
| Control variables | ||||||||
| Number of past publications | 1.002** | 0.0006 | 1.002*** | 0.0006 | 1.0001 | 0.0005 | 1.002*** ** | 0.0005 |
| Gender | 1.077 | 0.059 | 1.072 | 0.059 | 1.070 | 0.081 | 1.076 | 0.063 |
| Physician status | 0.816*** | 0.045 | 0.822** | 0.048 | 0.801*** | 0.045 | 0.815*** | 0.046 |
| Senior lecturer | 1.057 | 0.083 | 1.042 | 0.090 | 1.023 | 0.090 | 1.726* | 0.437 |
| Reader | 1.116 | 0.117 | 1.097 | 0.105 | 1.123 | 0.122 | 1.954* | 0.526 |
| Professor | 1.522*** | 0.129 | 1.509*** | 0.123 | 1.502*** | 0.139 | 2.561*** | 0.662 |
| Solo versus multiple authorship | ||||||||
| Solo-authored articles | 1.010 | 0.015 | 1.009 | 0.015 | 1.013 | 0.012 | 1.007 | 0.015 |
| Median number of co-authors per publication | 1.034** | 0.012 | 1.032* | 0.013 | 1.071*** | 0.014 | 1.030* | 0.012 |
| (Median number of co-authors per publication)2 | 0.997** | 0.0008 | 0.997*** | 0.0008 | 0.997** | 0.0009 | 0.997*** | 0.0007 |
| Minimum number of co-authors per publication | 0.968 | 0.0008 | 0.968* | 0.016 | 0.948** | 0.017 | 0.964* | 0.016 |
| Network-based measures of centrality | ||||||||
| Degree | 678.052*** ** | 1158.870 | 937.552*** | 1420.734 | ||||
| Eigenvector | 8.986* | 9.488 | ||||||
| Betweenness | 1.433* | 0.256 | ||||||
| Closeness | 8.57e+88*** | 8.71e+89 | ||||||
| Network-based measures of social capital | ||||||||
| Clustering coefficient | 0.455*** | 0.052 | ||||||
| Constraint | 0.377** | 0.137 | 0.342** | 0.120 | 0.319*** | 0.077 | ||
| Author's position in publication | ||||||||
| Position in non-alphabetised bylines: | ||||||||
| First | 1.045*** | 0.011 | 1.045*** | 0.012 | 1.042*** | 0.010 | 1.047*** | 0.010 |
| Last | 1.019* | 0.009 | 1.019* | 0.008 | 1.021*** | 0.006 | 0.870* | 0.055 |
| Second | 1.012 | 0.016 | 1.012 | 0.017 | 1.022 | 0.014 | 1.019 | 0.018 |
| Penultimate | 0.990 | 0.010 | 0.989 | 0.008 | 0.997 | 0.007 | 0.991 | 0.008 |
| Other | 1.020** | 0.007 | 1.023*** | 0.006 | 1.021*** | 0.005 | 1.022** | 0.008 |
| Position in alphabetised bylines: | ||||||||
| First | 1.094*** | 0.025 | 1.092** | 0.032 | 1.077* | 0.032 | 1.088* | 0.042 |
| Last | 1.014 | 0.023 | 1.014 | 1.023 | 0.022 | 0.023 | 1.020 | 0.023 |
| Second | 1.037 | 0.054 | 1.037 | 0.050 | 1.055 | 0.051 | 0.032 | 0.055 |
| Penultimate | 0.938 | 0.108 | 0.899 | 0.097 | 0.932 | 0.085 | 0.935 | 0.094 |
| Other | 1.126 | 0.165 | 1.142 | 0.135 | 1.070 | 0.163 | 1.103 | 0.162 |
| Interactions: academic rank and position | ||||||||
| Senior lecturer × non-alphabetical last position | 1.136* | 0.070 | ||||||
| Reader × non-alphabetical last position | 1.107 | 0.078 | ||||||
| Professor × non-alphabetical last position | 1.206** | 0.077 | ||||||
| Senior lecturer × alphabetical first position | 1.090 | 0.086 | ||||||
| Reader × alphabetical first position | 0.926 | 0.076 | ||||||
| Professor × alphabetical first position | 1.004 | 0.050 | ||||||
| Interactions: academic rank, position and brokerage | ||||||||
| Senior lecturer × non-alphabetical last position × constraint | 0.890 | 0.128 | ||||||
| Reader × non-alphabetical last position × constraint | 1.048 | 0.161 | ||||||
| Professor × non-alphabetical last position × constraint | 1.277*** | 0.079 | ||||||
Note: For ease of interpretation, the table displays incidence rate ratios. Models (1), (2) and (3) include only the main effects of the independent variables on authors’ performance: Model (1) includes degree and constraint; Model (2) eigenvector centrality, betweenness centrality and constraint and Model (3) closeness centrality and the clustering coefficient (please refer to the main text and the Supplementary Appendix for the definition of these network measures). Model 4 includes interaction effects between independent variables. The reference category for academic rank is ‘lecturer’. EC: estimated coefficient; SE: bootstrap standard error.
*p < 0.05; **p < 0.01; ***p < 0.001.