| Value | Category | Cases | |
|---|---|---|---|
| 1 | 1 yr or less | 105 |
6.6%
|
| 2 | between 1 and 2 yrs | 72 |
4.5%
|
| 3 | more than 2 yrs | 212 |
13.3%
|
| 4 | never | 1201 |
75.3%
|
| 77 | don't know | 4 |
0.3%
|
| Sysmiss | 1068 |