| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 0 | 
                                    
                                    0%
                                 | 
| 2005 | 1 | 
                                    
                                    12.5%
                                 | |
| 2013 | 2 | 
                                    
                                    25%
                                 | |
| 2016 | 2 | 
                                    
                                    25%
                                 | |
| 2018 | 3 | 
                                    
                                    37.5%
                                 | |
| Sysmiss | 149 |