| Value | Category | Cases | |
|---|---|---|---|
| 99 | Mising | 0 |
0%
|
| 1988 | 1 |
33.3%
|
|
| 1998 | 1 |
33.3%
|
|
| 2007 | 1 |
33.3%
|
|
| Sysmiss | 1722 |