| Value | Category | Cases | |
|---|---|---|---|
| 1 | At once | 15 |
19.5%
|
| 2 | Within a month | 6 |
7.8%
|
| 3 | Later than a month | 5 |
6.5%
|
| 4 | Don't know | 51 |
66.2%
|
| Sysmiss | 4467 |