| 1997 | 2000 | 2004 | 2006 | 2009 | 2011 | |
| farmer | 11.27% | 10.51% | 16.30% | 18.10% | 12.05% | 17.65% |
| Senior technicians | 45.99% | 43.83% | 35.48% | 44.92% | 54.04% | 64.37% |
| Generaltechnicians | 30.48% | 47.62% | 26.92% | 45.05% | 42.47% | 50.32% |
| Skill mechanic | 33.73% | 40.56% | 49.42% | 47.60% | 36.95% | 43.02% |
| Unskilled mechanic | 20.28% | 22.60% | 27.85% | 26.15% | 24.34% | 30.16% |
| Manager | 55.64% | 67.97% | 30.23% | 37.57% | 36.07% | 45.92% |
| Service trade | 26.43% | 29.78% | 39.49% | 41.78% | 34.45% | 44.39% |
| Other | 35.16% | 16.53% | 28.37% | 37.80% | 31.73% | 40.50% |