| Study | Sample size | Region | Age (years) | Volume (ml) | Sperm concentration (million/ml) | Total sperm concentration (million) | Normokinesis (%) | Total sperm motility (%) | Morphology (%) |
| Artur Wdowiak et al. (2016) (16) | 3266 | Poland | 32.28 | - | 36.33 | 145.69 | 19.48 | - | 16.65 |
| 3012 | Ukraine | 32.93 | - | 36.02 | 123.75 | 27.43 | - | 24.36 | |
| Jiang et al. (2013) (17) | 28,213 | China (Sichuan) | 32 | 2.5 | 65.6 | - | 38.4 | 53.8 | 9.5 |
| Li et al. (2007) (18)a | 1346 | China (Chongqing) | 20 - 40b | 2.5 | 84.8 | 203.2 | 51.5 | 67.3 | - |
| Paasch et al. (2007) (6) | 457 | Germany (Leipzig) | 18.9 | 2.7 | 65 | 166 | - | 77 | 8.3 |
| 334 | Germany (Hamburg) | 19.7 | 3.4 | 63 | 206 | - | 66 | 9.3 | |
| Jónrit Halling et al. (2013) (19) | 481 | Faroe Islands | 24 | 4.1 | 57 | 215 | - | 64 | 6.9 |
| Mendiola et al. (2012) (20) | 215 | Spain (Murcia) | 19.2 | 3.3 | 52.1 | 154 | - | 56.5 | 10.3 |
| Cok et al. (2015) (21)a | 658 | Turkey | 18 - 30b | 4.1 | 75.34 | 286.76 | 64 | 64.8 | - |
| Axelsson et al. (2011) (22)a | 295 | Sweden | 18 | 2.9 | 71 | 210 | 53 | - | - |
| Jørgensen et al. (2012) (23)a | 1274 | Denmark (Copenhagen) | 19.0 | 3.6 | 62 | 206 | 57 | 65 | 7.5 |