| Value | Category | Cases | |
|---|---|---|---|
| 0 | Never absent | 990 |
51.6%
|
| 1 | Less than 3 months | 736 |
38.4%
|
| 2 | 3-6 months | 101 |
5.3%
|
| 3 | 6-9 months | 36 |
1.9%
|
| 4 | More than 9 months | 55 |
2.9%
|
| Sysmiss | 3857 |