| Value | Category | Cases | |
|---|---|---|---|
| 1 | At once | 155 |
26.1%
|
| 2 | Within a month | 63 |
10.6%
|
| 3 | Later than a month | 70 |
11.8%
|
| 4 | Don't know | 305 |
51.4%
|
| Sysmiss | 3951 |