| Value | Category | Cases | |
|---|---|---|---|
| 1 | month | 8 |
80%
|
| 2 | year | 2 |
20%
|
| 77 | refused | 0 |
0%
|
| 88 | don't know | 0 |
0%
|
| 99 | missing | 0 |
0%
|
| Sysmiss | 4960 |