Ratio | Melnis and Knets [18] | McElhaney [1] | Crowninshield and Pope [4] |
| 25% | 25% | 28% |
| 11% | 11% | 12% |
| 5% | 4% | 3% |
| 10% | 10% | 9% |
| 49% | 50% | 48% |