| Value | Category | Cases | |
|---|---|---|---|
| 1 | 1 yr or less | 26 |
3.9%
|
| 2 | between 1 and 2 yrs | 30 |
4.5%
|
| 3 | more than 2 yrs | 67 |
10%
|
| 4 | never | 531 |
79.5%
|
| 77 | don't know | 14 |
2.1%
|
| Sysmiss | 461 |