| Value | Category | Cases | |
|---|---|---|---|
| 1980 | 1 | 
                                    
                                    0%
                                 | |
| 1985 | 1 | 
                                    
                                    0%
                                 | |
| 1986 | 7 | 
                                    
                                    0.1%
                                 | |
| 1987 | 11 | 
                                    
                                    0.2%
                                 | |
| 1988 | 27 | 
                                    
                                    0.6%
                                 | |
| 1989 | 33 | 
                                    
                                    0.7%
                                 | |
| 1990 | 52 | 
                                    
                                    1.1%
                                 | |
| 1991 | 47 | 
                                    
                                    1%
                                 | |
| 1992 | 70 | 
                                    
                                    1.4%
                                 | |
| 1993 | 78 | 
                                    
                                    1.6%
                                 | |
| 1994 | 92 | 
                                    
                                    1.9%
                                 | |
| 1995 | 86 | 
                                    
                                    1.8%
                                 | |
| 1996 | 94 | 
                                    
                                    1.9%
                                 | |
| 1997 | 115 | 
                                    
                                    2.4%
                                 | |
| 1998 | 123 | 
                                    
                                    2.5%
                                 | |
| 1999 | 103 | 
                                    
                                    2.1%
                                 | |
| 2000 | 140 | 
                                    
                                    2.9%
                                 | |
| 2001 | 131 | 
                                    
                                    2.7%
                                 | |
| 2002 | 142 | 
                                    
                                    2.9%
                                 | |
| 2003 | 143 | 
                                    
                                    2.9%
                                 | |
| 2004 | 142 | 
                                    
                                    2.9%
                                 | |
| 2005 | 124 | 
                                    
                                    2.5%
                                 | |
| 2006 | 161 | 
                                    
                                    3.3%
                                 | |
| 2007 | 164 | 
                                    
                                    3.4%
                                 | |
| 2008 | 183 | 
                                    
                                    3.7%
                                 | |
| 2009 | 180 | 
                                    
                                    3.7%
                                 | |
| 2010 | 219 | 
                                    
                                    4.5%
                                 | |
| 2011 | 206 | 
                                    
                                    4.2%
                                 | |
| 2012 | 245 | 
                                    
                                    5%
                                 | |
| 2013 | 235 | 
                                    
                                    4.8%
                                 | |
| 2014 | 328 | 
                                    
                                    6.7%
                                 | |
| 2015 | 318 | 
                                    
                                    6.5%
                                 | |
| 2016 | 291 | 
                                    
                                    6%
                                 | |
| 2017 | 302 | 
                                    
                                    6.2%
                                 | |
| 2018 | 267 | 
                                    
                                    5.5%
                                 | |
| 2019 | 8 | 
                                    
                                    0.2%
                                 | |
| 9999 | NO RESPONSE | 18 | 
                                    
                                    0.4%
                                 |