| Value | Category | Cases | |
|---|---|---|---|
| 1960 | 1 | 
                                                                 
                                    
                                    0.3%
                                 
                                                             | 
                                                        
                    |
| 1968 | 1 | 
                                                                 
                                    
                                    0.3%
                                 
                                                             | 
                                                        
                    |
| 1979 | 1 | 
                                                                 
                                    
                                    0.3%
                                 
                                                             | 
                                                        
                    |
| 1982 | 2 | 
                                                                 
                                    
                                    0.6%
                                 
                                                             | 
                                                        
                    |
| 1983 | 1 | 
                                                                 
                                    
                                    0.3%
                                 
                                                             | 
                                                        
                    |
| 1984 | 1 | 
                                                                 
                                    
                                    0.3%
                                 
                                                             | 
                                                        
                    |
| 1985 | 1 | 
                                                                 
                                    
                                    0.3%
                                 
                                                             | 
                                                        
                    |
| 1986 | 3 | 
                                                                 
                                    
                                    0.9%
                                 
                                                             | 
                                                        
                    |
| 1988 | 1 | 
                                                                 
                                    
                                    0.3%
                                 
                                                             | 
                                                        
                    |
| 1989 | 3 | 
                                                                 
                                    
                                    0.9%
                                 
                                                             | 
                                                        
                    |
| 1990 | 2 | 
                                                                 
                                    
                                    0.6%
                                 
                                                             | 
                                                        
                    |
| 1992 | 2 | 
                                                                 
                                    
                                    0.6%
                                 
                                                             | 
                                                        
                    |
| 1993 | 1 | 
                                                                 
                                    
                                    0.3%
                                 
                                                             | 
                                                        
                    |
| 1994 | 4 | 
                                                                 
                                    
                                    1.2%
                                 
                                                             | 
                                                        
                    |
| 1995 | 3 | 
                                                                 
                                    
                                    0.9%
                                 
                                                             | 
                                                        
                    |
| 1996 | 3 | 
                                                                 
                                    
                                    0.9%
                                 
                                                             | 
                                                        
                    |
| 1997 | 7 | 
                                                                 
                                    
                                    2.1%
                                 
                                                             | 
                                                        
                    |
| 1998 | 7 | 
                                                                 
                                    
                                    2.1%
                                 
                                                             | 
                                                        
                    |
| 1999 | 7 | 
                                                                 
                                    
                                    2.1%
                                 
                                                             | 
                                                        
                    |
| 2000 | 15 | 
                                                                 
                                    
                                    4.5%
                                 
                                                             | 
                                                        
                    |
| 2001 | 14 | 
                                                                 
                                    
                                    4.2%
                                 
                                                             | 
                                                        
                    |
| 2002 | 15 | 
                                                                 
                                    
                                    4.5%
                                 
                                                             | 
                                                        
                    |
| 2003 | 6 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 2004 | 10 | 
                                                                 
                                    
                                    3%
                                 
                                                             | 
                                                        
                    |
| 2005 | 9 | 
                                                                 
                                    
                                    2.7%
                                 
                                                             | 
                                                        
                    |
| 2006 | 14 | 
                                                                 
                                    
                                    4.2%
                                 
                                                             | 
                                                        
                    |
| 2007 | 16 | 
                                                                 
                                    
                                    4.8%
                                 
                                                             | 
                                                        
                    |
| 2008 | 23 | 
                                                                 
                                    
                                    6.9%
                                 
                                                             | 
                                                        
                    |
| 2009 | 22 | 
                                                                 
                                    
                                    6.6%
                                 
                                                             | 
                                                        
                    |
| 2010 | 16 | 
                                                                 
                                    
                                    4.8%
                                 
                                                             | 
                                                        
                    |
| 2011 | 22 | 
                                                                 
                                    
                                    6.6%
                                 
                                                             | 
                                                        
                    |
| 2012 | 23 | 
                                                                 
                                    
                                    6.9%
                                 
                                                             | 
                                                        
                    |
| 2013 | 14 | 
                                                                 
                                    
                                    4.2%
                                 
                                                             | 
                                                        
                    |
| 2014 | 17 | 
                                                                 
                                    
                                    5.1%
                                 
                                                             | 
                                                        
                    |
| 2015 | 17 | 
                                                                 
                                    
                                    5.1%
                                 
                                                             | 
                                                        
                    |
| 2016 | 20 | 
                                                                 
                                    
                                    6%
                                 
                                                             | 
                                                        
                    |
| 2017 | 6 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 2018 | 3 | 
                                                                 
                                    
                                    0.9%
                                 
                                                             |