| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 9 | 
                                    
                                    22.5%
                                 | 
| 1950 | 2 | 
                                    
                                    5%
                                 | |
| 1980 | 1 | 
                                    
                                    2.5%
                                 | |
| 1982 | 1 | 
                                    
                                    2.5%
                                 | |
| 1985 | 1 | 
                                    
                                    2.5%
                                 | |
| 1989 | 2 | 
                                    
                                    5%
                                 | |
| 1990 | 2 | 
                                    
                                    5%
                                 | |
| 1991 | 1 | 
                                    
                                    2.5%
                                 | |
| 1992 | 1 | 
                                    
                                    2.5%
                                 | |
| 1995 | 1 | 
                                    
                                    2.5%
                                 | |
| 1996 | 1 | 
                                    
                                    2.5%
                                 | |
| 1998 | 2 | 
                                    
                                    5%
                                 | |
| 2000 | 1 | 
                                    
                                    2.5%
                                 | |
| 2004 | 1 | 
                                    
                                    2.5%
                                 | |
| 2005 | 2 | 
                                    
                                    5%
                                 | |
| 2007 | 1 | 
                                    
                                    2.5%
                                 | |
| 2015 | 3 | 
                                    
                                    7.5%
                                 | |
| 2016 | 1 | 
                                    
                                    2.5%
                                 | |
| 2017 | 1 | 
                                    
                                    2.5%
                                 | |
| 2018 | 1 | 
                                    
                                    2.5%
                                 | |
| 2019 | 1 | 
                                    
                                    2.5%
                                 | |
| 2021 | 1 | 
                                    
                                    2.5%
                                 | |
| 2022 | 1 | 
                                    
                                    2.5%
                                 | |
| 2023 | 1 | 
                                    
                                    2.5%
                                 | |
| 2024 | 1 | 
                                    
                                    2.5%
                                 | |
| Sysmiss | 175 |