| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 21 | 
                                    
                                    9.1%
                                 | 
| 0 | None | 182 | 
                                    
                                    78.4%
                                 | 
| 1 | 18 | 
                                    
                                    7.8%
                                 | |
| 2 | 2 | 
                                    
                                    0.9%
                                 | |
| 3 | 2 | 
                                    
                                    0.9%
                                 | |
| 4 | 2 | 
                                    
                                    0.9%
                                 | |
| 5 | 2 | 
                                    
                                    0.9%
                                 | |
| 10 | 3 | 
                                    
                                    1.3%
                                 | |
| Sysmiss | 380 |