| Value | Category | Cases | |
|---|---|---|---|
| -2 | don't know | 2 |
20%
|
| 1985 | 1 |
10%
|
|
| 1987 | 1 |
10%
|
|
| 1990 | 1 |
10%
|
|
| 1996 | 1 |
10%
|
|
| 2002 | 1 |
10%
|
|
| 2006 | 2 |
20%
|
|
| 2009 | 1 |
10%
|
|
| Sysmiss | 1039 |