| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 4 | 
                                    
                                    0.3%
                                 | 
| 1 | Yes | 460 | 
                                    
                                    32.5%
                                 | 
| 2 | No | 952 | 
                                    
                                    67.2%
                                 |