| Value | Category | Cases | |
|---|---|---|---|
| 1980 | 4 | 
                                    
                                    0%
                                 | |
| 1981 | 7 | 
                                    
                                    0%
                                 | |
| 1982 | 12 | 
                                    
                                    0.1%
                                 | |
| 1983 | 12 | 
                                    
                                    0.1%
                                 | |
| 1984 | 12 | 
                                    
                                    0.1%
                                 | |
| 1985 | 29 | 
                                    
                                    0.2%
                                 | |
| 1986 | 48 | 
                                    
                                    0.3%
                                 | |
| 1987 | 55 | 
                                    
                                    0.4%
                                 | |
| 1988 | 73 | 
                                    
                                    0.5%
                                 | |
| 1989 | 71 | 
                                    
                                    0.5%
                                 | |
| 1990 | 100 | 
                                    
                                    0.7%
                                 | |
| 1991 | 98 | 
                                    
                                    0.7%
                                 | |
| 1992 | 118 | 
                                    
                                    0.8%
                                 | |
| 1993 | 135 | 
                                    
                                    0.9%
                                 | |
| 1994 | 150 | 
                                    
                                    1%
                                 | |
| 1995 | 132 | 
                                    
                                    0.9%
                                 | |
| 1996 | 141 | 
                                    
                                    1%
                                 | |
| 1997 | 161 | 
                                    
                                    1.1%
                                 | |
| 1998 | 213 | 
                                    
                                    1.5%
                                 | |
| 1999 | 156 | 
                                    
                                    1.1%
                                 | |
| 2000 | 256 | 
                                    
                                    1.8%
                                 | |
| 2001 | 176 | 
                                    
                                    1.2%
                                 | |
| 2002 | 214 | 
                                    
                                    1.5%
                                 | |
| 2003 | 202 | 
                                    
                                    1.4%
                                 | |
| 2004 | 188 | 
                                    
                                    1.3%
                                 | |
| 2005 | 245 | 
                                    
                                    1.7%
                                 | |
| 2006 | 262 | 
                                    
                                    1.8%
                                 | |
| 2007 | 318 | 
                                    
                                    2.2%
                                 | |
| 2008 | 308 | 
                                    
                                    2.2%
                                 | |
| 2009 | 276 | 
                                    
                                    1.9%
                                 | |
| 2010 | 348 | 
                                    
                                    2.4%
                                 | |
| 2011 | 311 | 
                                    
                                    2.2%
                                 | |
| 2012 | 335 | 
                                    
                                    2.3%
                                 | |
| 2013 | 322 | 
                                    
                                    2.3%
                                 | |
| 2014 | 325 | 
                                    
                                    2.3%
                                 | |
| 2015 | 387 | 
                                    
                                    2.7%
                                 | |
| 2016 | 343 | 
                                    
                                    2.4%
                                 | |
| 2017 | 418 | 
                                    
                                    2.9%
                                 | |
| 2018 | 80 | 
                                    
                                    0.6%
                                 | |
| 9997 | INCONSISTENT | 379 | 
                                    
                                    2.7%
                                 | 
| 9998 | DK | 2338 | 
                                    
                                    16.4%
                                 | 
| 9999 | NO RESPONSE | 2 | 
                                    
                                    0%
                                 | 
| Sysmiss | 4537 | 
                                    
                                    31.7%
                                 |