| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 33 | 
                                    
                                    2.3%
                                 | 
| -7 | Never regiestered (spontaneous) | 0 | 
                                    
                                    0%
                                 | 
| 1937 | 1 | 
                                    
                                    0.1%
                                 | |
| 1940 | 1 | 
                                    
                                    0.1%
                                 | |
| 1948 | 1 | 
                                    
                                    0.1%
                                 | |
| 1950 | 2 | 
                                    
                                    0.1%
                                 | |
| 1952 | 1 | 
                                    
                                    0.1%
                                 | |
| 1953 | 2 | 
                                    
                                    0.1%
                                 | |
| 1956 | 1 | 
                                    
                                    0.1%
                                 | |
| 1957 | 1 | 
                                    
                                    0.1%
                                 | |
| 1960 | 2 | 
                                    
                                    0.1%
                                 | |
| 1963 | 1 | 
                                    
                                    0.1%
                                 | |
| 1964 | 1 | 
                                    
                                    0.1%
                                 | |
| 1967 | 2 | 
                                    
                                    0.1%
                                 | |
| 1968 | 2 | 
                                    
                                    0.1%
                                 | |
| 1969 | 1 | 
                                    
                                    0.1%
                                 | |
| 1970 | 2 | 
                                    
                                    0.1%
                                 | |
| 1971 | 1 | 
                                    
                                    0.1%
                                 | |
| 1972 | 5 | 
                                    
                                    0.4%
                                 | |
| 1973 | 1 | 
                                    
                                    0.1%
                                 | |
| 1974 | 2 | 
                                    
                                    0.1%
                                 | |
| 1975 | 2 | 
                                    
                                    0.1%
                                 | |
| 1976 | 1 | 
                                    
                                    0.1%
                                 | |
| 1977 | 1 | 
                                    
                                    0.1%
                                 | |
| 1978 | 1 | 
                                    
                                    0.1%
                                 | |
| 1979 | 4 | 
                                    
                                    0.3%
                                 | |
| 1980 | 9 | 
                                    
                                    0.6%
                                 | |
| 1981 | 2 | 
                                    
                                    0.1%
                                 | |
| 1982 | 7 | 
                                    
                                    0.5%
                                 | |
| 1983 | 5 | 
                                    
                                    0.4%
                                 | |
| 1984 | 6 | 
                                    
                                    0.4%
                                 | |
| 1985 | 8 | 
                                    
                                    0.6%
                                 | |
| 1986 | 6 | 
                                    
                                    0.4%
                                 | |
| 1987 | 11 | 
                                    
                                    0.8%
                                 | |
| 1988 | 6 | 
                                    
                                    0.4%
                                 | |
| 1989 | 9 | 
                                    
                                    0.6%
                                 | |
| 1990 | 12 | 
                                    
                                    0.8%
                                 | |
| 1991 | 2 | 
                                    
                                    0.1%
                                 | |
| 1992 | 18 | 
                                    
                                    1.3%
                                 | |
| 1993 | 19 | 
                                    
                                    1.3%
                                 | |
| 1994 | 20 | 
                                    
                                    1.4%
                                 | |
| 1995 | 30 | 
                                    
                                    2.1%
                                 | |
| 1996 | 18 | 
                                    
                                    1.3%
                                 | |
| 1997 | 19 | 
                                    
                                    1.3%
                                 | |
| 1998 | 34 | 
                                    
                                    2.4%
                                 | |
| 1999 | 7 | 
                                    
                                    0.5%
                                 | |
| 2000 | 50 | 
                                    
                                    3.5%
                                 | |
| 2001 | 37 | 
                                    
                                    2.6%
                                 | |
| 2002 | 42 | 
                                    
                                    3%
                                 | |
| 2003 | 27 | 
                                    
                                    1.9%
                                 | |
| 2004 | 47 | 
                                    
                                    3.3%
                                 | |
| 2005 | 49 | 
                                    
                                    3.5%
                                 | |
| 2006 | 28 | 
                                    
                                    2%
                                 | |
| 2007 | 35 | 
                                    
                                    2.5%
                                 | |
| 2008 | 48 | 
                                    
                                    3.4%
                                 | |
| 2009 | 46 | 
                                    
                                    3.2%
                                 | |
| 2010 | 58 | 
                                    
                                    4.1%
                                 | |
| 2011 | 45 | 
                                    
                                    3.2%
                                 | |
| 2012 | 44 | 
                                    
                                    3.1%
                                 | |
| 2013 | 42 | 
                                    
                                    3%
                                 | |
| 2014 | 63 | 
                                    
                                    4.4%
                                 | |
| 2015 | 76 | 
                                    
                                    5.4%
                                 | |
| 2016 | 71 | 
                                    
                                    5%
                                 | |
| 2017 | 52 | 
                                    
                                    3.7%
                                 | |
| 2018 | 63 | 
                                    
                                    4.4%
                                 | |
| 2019 | 53 | 
                                    
                                    3.7%
                                 | |
| 2020 | 57 | 
                                    
                                    4%
                                 | |
| 2021 | 37 | 
                                    
                                    2.6%
                                 | |
| 2022 | 18 | 
                                    
                                    1.3%
                                 | |
| 2023 | 7 | 
                                    
                                    0.5%
                                 | |
| 2024 | 1 | 
                                    
                                    0.1%
                                 |