| Value | Category | Cases | |
|---|---|---|---|
| -2 | Refusal to answer | 1 |
2.8%
|
| -1 | Don't know | 2 |
5.6%
|
| 1960 | 1 |
2.8%
|
|
| 1980 | 2 |
5.6%
|
|
| 1990 | 1 |
2.8%
|
|
| 1991 | 1 |
2.8%
|
|
| 1992 | 3 |
8.3%
|
|
| 1994 | 2 |
5.6%
|
|
| 1996 | 2 |
5.6%
|
|
| 1997 | 2 |
5.6%
|
|
| 1998 | 5 |
13.9%
|
|
| 1999 | 8 |
22.2%
|
|
| 2000 | 6 |
16.7%
|
|
| Sysmiss | 2597 |