Estimates of linear models for the log impact of articles with fixed effects for the journals overall_
| Coef. | Std Err. | t | P>t | [95% Conf. Interval] | |||
|---|---|---|---|---|---|---|---|
| X1 | (log) n. authors | 0.085 | 0.001 | 66.1 | <0.01 | 0.082 | 0.087 |
| X2 | (log) n. countries | 0.041 | 0.002 | 24.4 | <0.01 | 0.037 | 0.044 |
| X3 | (log) avg authors quality | 0.224 | 0.001 | 242.3 | <0.01 | 0.222 | 0.226 |
| X4 | Women | -0.024 | 0.001 | -17.1 | <0.01 | -0.026 | -0.021 |
| X5 | English | -0.022 | 0.002 | -15.0 | <0.01 | -0.025 | -0.020 |
| X6 | open access | 0.070 | 0.002 | 38.5 | <0.01 | 0.066 | 0.073 |
| X7 | (log) n. pages | 0.200 | 0.002 | 86.8 | <0.01 | 0.195 | 0.204 |
| X8 | (log) n. references | 0.268 | 0.002 | 165.8 | <0.01 | 0.265 | 0.271 |
| X9 | % references in WoS | 0.002 | 0.000 | 39.2 | <0.01 | 0.002 | 0.002 |
| X10 | (log) cited articles age | -0.374 | 0.002 | -231.6 | <0.01 | -0.377 | -0.370 |
| X11 | (log) cited articles impact | 0.061 | 0.001 | 97.5 | <0.01 | 0.060 | 0.063 |
| Intercept | -1.436 | 0.007 | -201.9 | <0.01 | -1.450 | -1.422 | |
Number of articles per area of the journal_
| Area | N. of articles | |
|---|---|---|
| 1 | Arts and Humanities | 17,816 |
| 2 | Biology | 251,921 |
| 3 | Biomedical Research | 164,805 |
| 4 | Chemistry | 194,405 |
| 5 | Clinical Medicine | 316,828 |
| 6 | Earth and Space Sciences | 116,736 |
| 7 | Economics | 40,308 |
| 8 | Engineering | 349,058 |
| 9 | Law, political and social sciences | 65,344 |
| 10 | Mathematics | 57,718 |
| 11 | Multidisciplinary Sciences | 66,985 |
| 12 | Physics | 227,595 |
| 13 | Psychology | 30,896 |
| Total | 1,900,415 |
Summary statistics of the variables of the dataset (1,427,670 articles)_
| Variable | Mean | Std dev. | Min | Max | |
|---|---|---|---|---|---|
| Y | impact | 0.871 | 1.992 | 0 | 1,039.638 |
| X1 | n. authors | 5.476 | 3.959 | 1 | 100 |
| X2 | n. countries | 1.417 | 0.894 | 1 | 44 |
| X3 | avg authors quality | 1.015 | 1.053 | 0.001 | 204.831 |
| X4 | Women | 0.605 | 0.489 | 0 | 1 |
| X5 | English | 0.395 | 0.489 | 0 | 1 |
| X6 | open access | 0.453 | 0.498 | 0 | 1 |
| X7 | n. pages | 11.000 | 6.259 | 1 | 100 |
| X8 | n. references | 41.317 | 22.570 | 1 | 200 |
| X9 | % references in WoS | 76.874 | 20.630 | 0.515 | 100 |
| X10 | cited articles age | 9.431 | 3.716 | 0 | 37 |
| X11 | cited articles impact | 11.800 | 23.462 | 0.010 | 1,995.620 |
Estimates of linear models for the log impact of the articles with fixed effects for the journals (standard errors in parenthesis)‡, by area_
| Area‡ | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| X1 (log) n. authors | 0.079 | 0.082 | 0.072 | 0.044 | 0.088 | 0.105 | 0.122 | 0.071 | 0.069 | 0.087 | 0.111 | 0.084 | 0.057 |
| (0.018) | (0.003) | (0.004) | (0.003) | (0.003) | (0.004) | (0.009) | (0.003) | (0.007) | (0.009) | (0.005) | (0.003) | (0.009) | |
| X2 (log) n. countries | 0.109 | 0.033 | 0.044 | 0.009† | 0.045 | 0.055 | 0.075 | 0.039 | 0.056 | 0.112 | -0.002† | 0.034 | 0.053 |
| (0.026) | (0.004) | (0.005) | (0.005) | (0.003) | (0.005) | (0.010) | (0.004) | (0.010) | (0.010) | (0.007) | (0.004) | (0.012) | |
| X3 (log) avg authors quality | 0.179 | 0.235 | 0.177 | 0.282 | 0.157 | 0.225 | 0.220 | 0.242 | 0.212 | 0.299 | 0.233 | 0.259 | 0.243 |
| (0.008) | (0.002) | (0.003) | (0.003) | (0.002) | (0.003) | (0.005) | (0.002) | (0.004) | (0.005) | (0.004) | (0.002) | (0.007) | |
| X4 Women | 0.024† | -0.034 | -0.016 | -0.023 | -0.017 | -0.053 | -0.013† | -0.028 | 0.011† | -0.044 | -0.007† | -0.023 | -0.011† |
| (0.017) | (0.003) | (0.004) | (0.003) | (0.003) | (0.004) | (0.008) | (0.003) | (0.008) | (0.008) | (0.006) | (0.003) | (0.011) | |
| X5 English | 0.020† | -0.023 | -0.019 | -0.044 | -0.005† | -0.054 | -0.038 | -0.033 | 0.017† | -0.052 | -0.002† | -0.014 | -0.008† |
| (0.017) | (0.003) | (0.004) | (0.004) | (0.003) | (0.005) | (0.009) | (0.003) | (0.008) | (0.008) | (0.006) | (0.004) | (0.010) | |
| X6 open access | 0.164 | 0.070 | 0.101 | 0.020 | 0.114 | 0.068 | 0.087 | 0.037 | 0.139 | 0.038 | 0.087 | 0.033 | 0.079 |
| (0.018) | (0.004) | (0.006) | (0.004) | (0.004) | (0.006) | (0.009) | (0.004) | (0.008) | (0.010) | (0.018) | (0.004) | (0.010) | |
| X7 (log) n. pages | 0.230 | 0.169 | 0.230 | 0.217 | 0.270 | 0.205 | 0.134 | 0.193 | 0.218 | 0.090 | 0.086 | 0.221 | 0.187 |
| (0.026) | (0.005) | (0.007) | (0.006) | (0.005) | (0.008) | (0.015) | (0.005) | (0.013) | (0.010) | (0.011) | (0.005) | (0.018) | |
| X8 (log) n. references | 0.269 | 0.277 | 0.239 | 0.249 | 0.243 | 0.267 | 0.313 | 0.268 | 0.275 | 0.316 | 0.287 | 0.262 | 0.291 |
| (0.017) | (0.004) | (0.005) | (0.004) | (0.003) | (0.006) | (0.010) | (0.003) | (0.008) | (0.008) | (0.008) | (0.004) | (0.012) | |
| X9 % references in WoS | 0.007 | 0.002 | 0.001 | 0.000† | 0.002 | 0.002 | 0.002 | 0.002 | 0.004 | 0.002 | -0.000† | 0.000 | 0.001 |
| (0.001) | (0.000) | (0.000) | (0.000) | (0.000) | (0.000) | (0.000) | (0.000) | (0.000) | (0.000) | (0.000) | (0.000) | (0.000) | |
| X10 (log) cited articles age | -0.193 | -0.408 | -0.383 | -0.456 | -0.319 | -0.414 | -0.490 | -0.386 | -0.322 | -0.357 | -0.429 | -0.395 | -0.463 |
| (0.013) | (0.004) | (0.005) | (0.004) | (0.004) | (0.006) | (0.011) | (0.003) | (0.008) | (0.009) | (0.008) | (0.004) | (0.015) | |
| X11 (log) cited articles impact | 0.093 | 0.043 | 0.070 | 0.029 | 0.075 | 0.090 | 0.127 | 0.076 | 0.096 | 0.103 | 0.051 | 0.045 | 0.093 |
| (0.008) | (0.001) | (0.002) | (0.001) | (0.001) | (0.003) | (0.005) | (0.001) | (0.004) | (0.004) | (0.003) | (0.002) | (0.005) | |
| Intercept | -2.312 | -1.264 | -1.377 | -0.952 | -1.676 | -1.409 | -1.308 | -1.326 | -1.821 | -1.303 | -1.160 | -1.269 | -1.266 |
| (0.071) | (0.017) | (0.021) | (0.021) | (0.015) | (0.025) | (0.047) | (0.015) | (0.036) | (0.037) | (0.038) | (0.018) | (0.056) | |
| Number of articles | 17,816 | 251,921 | 164,805 | 194,405 | 316,828 | 116,736 | 40,308 | 349,058 | 65,344 | 57,718 | 66,985 | 227,595 | 30,896 |
| Number of journals | 1,618 | 2,187 | 1,187 | 600 | 2,954 | 931 | 919 | 2,104 | 1,800 | 746 | 202 | 864 | 525 |
| R-squared | 0.26 | 0.27 | 0.26 | 0.31 | 0.24 | 0.27 | 0.28 | 0.28 | 0.22 | 0.26 | 0.24 | 0.30 | 0.22 |
| Intra-journal correlation | 0.32 | 0.27 | 0.29 | 0.34 | 0.28 | 0.24 | 0.26 | 0.28 | 0.25 | 0.18 | 0.39 | 0.26 | 0.26 |