| Value | Category | Cases | |
|---|---|---|---|
| 1 | 1 yr or less | 79 |
3.7%
|
| 2 | between 1 and 2 yrs | 26 |
1.2%
|
| 3 | more than 2 yrs | 135 |
6.3%
|
| 4 | never | 1849 |
86.8%
|
| 77 | don't know | 42 |
2%
|
| Sysmiss | 1677 |