| Value | Category | Cases | |
|---|---|---|---|
| -99 | Don't know | 498 |
12%
|
| 1988 | 1988 | 7 |
0.2%
|
| 1989 | 1989 | 5 |
0.1%
|
| 1990 | 1990 | 6 |
0.1%
|
| 1991 | 1991 | 11 |
0.3%
|
| 1992 | 1992 | 24 |
0.6%
|
| 1993 | 1993 | 21 |
0.5%
|
| 1994 | 1994 | 33 |
0.8%
|
| 1995 | 1995 | 48 |
1.2%
|
| 1996 | 1996 | 65 |
1.6%
|
| 1997 | 1997 | 79 |
1.9%
|
| 1998 | 1998 | 85 |
2.1%
|
| 1999 | 1999 | 99 |
2.4%
|
| 2000 | 2000 | 136 |
3.3%
|
| 2001 | 2001 | 130 |
3.1%
|
| 2002 | 2002 | 168 |
4.1%
|
| 2003 | 2003 | 173 |
4.2%
|
| 2004 | 2004 | 156 |
3.8%
|
| 2005 | 2005 | 180 |
4.3%
|
| 2006 | 2006 | 210 |
5.1%
|
| 2007 | 2007 | 192 |
4.6%
|
| 2008 | 2008 | 193 |
4.7%
|
| 2009 | 2009 | 203 |
4.9%
|
| 2010 | 2010 | 227 |
5.5%
|
| 2011 | 2011 | 199 |
4.8%
|
| 2012 | 2012 | 215 |
5.2%
|
| 2013 | 2013 | 214 |
5.2%
|
| 2014 | 2014 | 250 |
6%
|
| 2015 | 2015 | 264 |
6.4%
|
| 2016 | 2016 | 54 |
1.3%
|
| Sysmiss | 3016 |