| Value | Category | Cases | |
|---|---|---|---|
| -2 | don't know | 67 |
53.2%
|
| 1961 | 1 |
0.8%
|
|
| 1970 | 3 |
2.4%
|
|
| 1975 | 4 |
3.2%
|
|
| 1980 | 11 |
8.7%
|
|
| 1985 | 9 |
7.1%
|
|
| 1986 | 1 |
0.8%
|
|
| 1988 | 2 |
1.6%
|
|
| 1989 | 1 |
0.8%
|
|
| 1990 | 8 |
6.3%
|
|
| 1991 | 2 |
1.6%
|
|
| 1992 | 1 |
0.8%
|
|
| 1993 | 1 |
0.8%
|
|
| 1995 | 1 |
0.8%
|
|
| 1997 | 2 |
1.6%
|
|
| 2000 | 1 |
0.8%
|
|
| 2002 | 1 |
0.8%
|
|
| 2003 | 1 |
0.8%
|
|
| 2005 | 1 |
0.8%
|
|
| 2006 | 3 |
2.4%
|
|
| 2007 | 3 |
2.4%
|
|
| 2008 | 1 |
0.8%
|
|
| 2009 | 1 |
0.8%
|
|
| Sysmiss | 923 |