| Country | Number of papers | |
| Total | % | |
| USA | 952 | 31.9 |
| UK | 362 | 12.1 |
| Canada | 230 | 7.7 |
| Australia | 216 | 7.2 |
| Netherlands | 166 | 5.6 |
| China | 92 | 3.1 |
| Germany | 83 | 2.8 |
| Turkey | 76 | 2.5 |
| Sweden | 67 | 2.2 |
| Taiwan | 67 | 2.2 |
| Spain | 56 | 1.9 |
| Singapore | 51 | 1.7 |
| Japan | 47 | 1.6 |
| South Africa | 45 | 1.5 |
| Brazil | 38 | 1.3 |
| Total | 2551 | 100 |