| Value | Category | Cases | |
|---|---|---|---|
| 1 | At once | 15 |
31.9%
|
| 2 | Within a month | 4 |
8.5%
|
| 3 | Later than a month | 5 |
10.6%
|
| 4 | Don't know | 23 |
48.9%
|
| Sysmiss | 4497 |