| Value | Category | Cases | |
|---|---|---|---|
| 1 | Within two years | 241 |
11%
|
| 2 | Within four years | 361 |
16.4%
|
| 3 | Within eight years | 305 |
13.9%
|
| 4 | More than eight years | 465 |
21.2%
|
| 5 | Never | 228 |
10.4%
|
| 9 | Don't know | 598 |
27.2%
|