| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 3 | 
                                                                 
                                    
                                    5.4%
                                 
                                                             | 
                                                        
                    
| 1955 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 1974 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 1981 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 1984 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 1986 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 1988 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 1990 | 3 | 
                                                                 
                                    
                                    5.4%
                                 
                                                             | 
                                                        
                    |
| 1992 | 3 | 
                                                                 
                                    
                                    5.4%
                                 
                                                             | 
                                                        
                    |
| 1993 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 1994 | 2 | 
                                                                 
                                    
                                    3.6%
                                 
                                                             | 
                                                        
                    |
| 1995 | 3 | 
                                                                 
                                    
                                    5.4%
                                 
                                                             | 
                                                        
                    |
| 1997 | 3 | 
                                                                 
                                    
                                    5.4%
                                 
                                                             | 
                                                        
                    |
| 1998 | 3 | 
                                                                 
                                    
                                    5.4%
                                 
                                                             | 
                                                        
                    |
| 1999 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 2000 | 3 | 
                                                                 
                                    
                                    5.4%
                                 
                                                             | 
                                                        
                    |
| 2001 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 2002 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 2004 | 3 | 
                                                                 
                                    
                                    5.4%
                                 
                                                             | 
                                                        
                    |
| 2005 | 5 | 
                                                                 
                                    
                                    8.9%
                                 
                                                             | 
                                                        
                    |
| 2008 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 2009 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 2010 | 4 | 
                                                                 
                                    
                                    7.1%
                                 
                                                             | 
                                                        
                    |
| 2013 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 2015 | 2 | 
                                                                 
                                    
                                    3.6%
                                 
                                                             | 
                                                        
                    |
| 2017 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 2018 | 1 | 
                                                                 
                                    
                                    1.8%
                                 
                                                             | 
                                                        
                    |
| 2019 | 2 | 
                                                                 
                                    
                                    3.6%
                                 
                                                             | 
                                                        
                    |
| 2021 | 2 | 
                                                                 
                                    
                                    3.6%
                                 
                                                             | 
                                                        
                    |
| Sysmiss | 332 |