Distribution of reviewed studies by country and publishing year intervals
| Number of studies by year intervals | |||
|---|---|---|---|
| Country | 1990–2000 | 2001–2010 | 2011–2013 |
| USA | 23 | 7 | 0 |
| UK | 7 | 2 | 0 |
| Sweden | 1 | 1 | 0 |
| Ireland | 0 | 1 | 0 |
| The Netherlands | 0 | 1 | 0 |
| Slovenia | 1 | 1 | 0 |
| Germany | 0 | 1 | 2 |
| Austria | 0 | 2 | 1 |
| Israel | 0 | 3 | 0 |
| Turkey | 0 | 1 | 0 |
| Pakistan | 0 | 1 | 0 |
| United Arab Emirates | 0 | 1 | 0 |
| Saudi Arabia | 0 | 1 | 0 |
| Australia | 1 | 1 | 1 |
| Hong Kong | 2 | 0 | 0 |
| South Africa | 1 | 0 | 0 |
| Total | 36 | 24 | 4 |