Types of incentives used stratified by continent (n=42)*
| Recruitment continent | N | Types of incentives used, n (%) | |||
| Compensation | Tokens of appreciation | Reimbursements | Payments | ||
| Africa | 3 | 2 (66.7) | 1 (33.3) | 1 (33.3) | 0 (0.0) |
| Asia | 1 | 0 (0.0) | 1 (100.0) | 0 (0.0) | 0 (0.0) |
| Australia | 3 | 1 (33.3) | 0 (0.0) | 2 (66.7) | 0 (0.0) |
| Europe | 2 | 2 (100.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) |
| North America | 33 | 16 (48.5) | 10 (30.3) | 2 (6.1) | 7 (21.2) |
| South America | 0 | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) |
*Some studies offered multiple types of incentives.