Country(s) of authors’ affiliation(s) using World Bank country income classifications for all authors, first, second and last authors
| Low-income countries | Lower middle-income countries | Upper middle-income countries | High-income countries | Mixed affiliations | P* | |
| All authors (N=14 111) | 1452 (10.3) | 3731 (26.4) | 2460 (17.4) | 5749 (40.7) | 721 (5.1) | |
| First author (N=1751) | 120 (6.9) | 417 (23.8) | 307 (17.5) | 767 (43.8) | 139 (7.9) | <0.001 |
| Second author (N=1657) | 153 (9.2) | 475 (28.7) | 310 (18.7) | 635 (38.3) | 84 (5.1) | <0.001 |
| Last author (N=1736) | 83 (4.8) | 359 (20.7) | 303 (17.5) | 838 (48.3) | 153 (8.8) | <0.001 |
Some articles had only a single author or two authors accounting for the different total N for first, second and last authors.
*Χ2.