Table 2.
Summary of geographic origin of the included studies
| Country | Number of studies | percentage |
|---|---|---|
| China | 193 | 58.3% |
| United States | 83 | 25.1% |
| United Kingdom | 8 | 2.4% |
| South Korea | 8 | 2.4% |
| Japan | 6 | 1.8% |
| Italy | 6 | 1.8% |
| Turkey | 5 | 1.5% |
| Others | 22 | 6.6% |
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