| Value | Category | Cases | |
|---|---|---|---|
| -2 | don't know | 3 |
42.9%
|
| 1970 | 1 |
14.3%
|
|
| 1980 | 2 |
28.6%
|
|
| 1990 | 1 |
14.3%
|
|
| Sysmiss | 1042 |