| 9 years |  8.6% |
| 8 years |  6.5% |
| 7 years |  10.4% |
| 6 years |  11.3% |
| 5 years |  16.3% |
| 4 years |  10.4% |
| 3 years |  11.3% |
| 2 years |  9.0% |
| 1 year |  5.7% |
| Less than a year |  6.6% |
| Don't know | 3.9% |
