| Quintiles | 1968 | 1973 | 1986 | 1994 | 2002 | 2003 | 2009 | 2017 |
| Lowest 20% | 3.0 | 3.5 | 3.9 | 4.86 | 5.3 | 6.0 | 5.6 | 6.3 |
| Next 20% | 7.0 | 8.0 | 8.4 | 8.63 | 9.8 | 10.3 | 10.3 | 10.7 |
| Next 20% | 10.0 | 12.5 | 12.60 | 12.91 | 14.0 | 14.5 | 15.1 | 14.8 |
| Next 20% | 20.0 | 19.5 | 19.20 | 19.03 | 20.8 | 20.9 | 21.5 | 20.9 |
| Highest 20% | 60.0 | 56.5 | 55.9 | 54.88 | 50.1 | 48.3 | 47.6 | 47.4 |
| Gini Coefficient | 0.56 | 0.51 | 0.46 | 0.49 | 0.44 | 0.42 | 0.41 | 0.40 |