| Value | Category | Cases | |
|---|---|---|---|
| 1 | 1 yr or less | 230 |
14.4%
|
| 2 | between 1 and 2 yrs | 72 |
4.5%
|
| 3 | more than 2 yrs | 195 |
12.2%
|
| 4 | never | 1079 |
67.7%
|
| 77 | don't know | 18 |
1.1%
|
| Sysmiss | 1068 |