| Value | Category | Cases | |
|---|---|---|---|
| 1 | Never | 7816 | 
                                                                 
                                    
                                    98.8%
                                 
                                                             | 
                                                        
                    
| 2 | Once | 29 | 
                                                                 
                                    
                                    0.4%
                                 
                                                             | 
                                                        
                    
| 3 | Several times | 59 | 
                                                                 
                                    
                                    0.7%
                                 
                                                             | 
                                                        
                    
| Sysmiss | 5 |