| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 103 | 
                                                                 
                                    
                                    12.4%
                                 
                                                             | 
                                                        
                    
| 1976 | 1 | 
                                                                 
                                    
                                    0.1%
                                 
                                                             | 
                                                        
                    |
| 1984 | 1 | 
                                                                 
                                    
                                    0.1%
                                 
                                                             | 
                                                        
                    |
| 1988 | 1 | 
                                                                 
                                    
                                    0.1%
                                 
                                                             | 
                                                        
                    |
| 1989 | 2 | 
                                                                 
                                    
                                    0.2%
                                 
                                                             | 
                                                        
                    |
| 1990 | 4 | 
                                                                 
                                    
                                    0.5%
                                 
                                                             | 
                                                        
                    |
| 1991 | 2 | 
                                                                 
                                    
                                    0.2%
                                 
                                                             | 
                                                        
                    |
| 1992 | 1 | 
                                                                 
                                    
                                    0.1%
                                 
                                                             | 
                                                        
                    |
| 1994 | 2 | 
                                                                 
                                    
                                    0.2%
                                 
                                                             | 
                                                        
                    |
| 1995 | 3 | 
                                                                 
                                    
                                    0.4%
                                 
                                                             | 
                                                        
                    |
| 1996 | 1 | 
                                                                 
                                    
                                    0.1%
                                 
                                                             | 
                                                        
                    |
| 1997 | 5 | 
                                                                 
                                    
                                    0.6%
                                 
                                                             | 
                                                        
                    |
| 1998 | 9 | 
                                                                 
                                    
                                    1.1%
                                 
                                                             | 
                                                        
                    |
| 1999 | 16 | 
                                                                 
                                    
                                    1.9%
                                 
                                                             | 
                                                        
                    |
| 2000 | 23 | 
                                                                 
                                    
                                    2.8%
                                 
                                                             | 
                                                        
                    |
| 2001 | 1 | 
                                                                 
                                    
                                    0.1%
                                 
                                                             | 
                                                        
                    |
| 2002 | 6 | 
                                                                 
                                    
                                    0.7%
                                 
                                                             | 
                                                        
                    |
| 2003 | 4 | 
                                                                 
                                    
                                    0.5%
                                 
                                                             | 
                                                        
                    |
| 2004 | 12 | 
                                                                 
                                    
                                    1.4%
                                 
                                                             | 
                                                        
                    |
| 2005 | 25 | 
                                                                 
                                    
                                    3%
                                 
                                                             | 
                                                        
                    |
| 2006 | 9 | 
                                                                 
                                    
                                    1.1%
                                 
                                                             | 
                                                        
                    |
| 2007 | 24 | 
                                                                 
                                    
                                    2.9%
                                 
                                                             | 
                                                        
                    |
| 2008 | 57 | 
                                                                 
                                    
                                    6.9%
                                 
                                                             | 
                                                        
                    |
| 2009 | 42 | 
                                                                 
                                    
                                    5.1%
                                 
                                                             | 
                                                        
                    |
| 2010 | 77 | 
                                                                 
                                    
                                    9.3%
                                 
                                                             | 
                                                        
                    |
| 2011 | 30 | 
                                                                 
                                    
                                    3.6%
                                 
                                                             | 
                                                        
                    |
| 2012 | 40 | 
                                                                 
                                    
                                    4.8%
                                 
                                                             | 
                                                        
                    |
| 2013 | 27 | 
                                                                 
                                    
                                    3.3%
                                 
                                                             | 
                                                        
                    |
| 2014 | 59 | 
                                                                 
                                    
                                    7.1%
                                 
                                                             | 
                                                        
                    |
| 2015 | 69 | 
                                                                 
                                    
                                    8.3%
                                 
                                                             | 
                                                        
                    |
| 2016 | 48 | 
                                                                 
                                    
                                    5.8%
                                 
                                                             | 
                                                        
                    |
| 2017 | 48 | 
                                                                 
                                    
                                    5.8%
                                 
                                                             | 
                                                        
                    |
| 2018 | 37 | 
                                                                 
                                    
                                    4.5%
                                 
                                                             | 
                                                        
                    |
| 2019 | 24 | 
                                                                 
                                    
                                    2.9%
                                 
                                                             | 
                                                        
                    |
| 2020 | 12 | 
                                                                 
                                    
                                    1.4%
                                 
                                                             | 
                                                        
                    |
| 2021 | 3 | 
                                                                 
                                    
                                    0.4%
                                 
                                                             | 
                                                        
                    |
| Sysmiss | 9844 |