| Value | Category | Cases | |
|---|---|---|---|
| 1 | Less than a year | 9 |
2.1%
|
| 2 | Years | 24 |
5.7%
|
| 3 | No specific period | 57 |
13.5%
|
| 9 | Missing | 333 |
78.7%
|
| 98 | Not applicable | 0 |
0%
|
| Sysmiss | 9004 |