| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 11 | 
                                    
                                    10.5%
                                 | 
| 1 | One month or less | 32 | 
                                    
                                    30.5%
                                 | 
| 2 | 12 | 
                                    
                                    11.4%
                                 | |
| 3 | 11 | 
                                    
                                    10.5%
                                 | |
| 4 | 5 | 
                                    
                                    4.8%
                                 | |
| 5 | 3 | 
                                    
                                    2.9%
                                 | |
| 6 | 11 | 
                                    
                                    10.5%
                                 | |
| 7 | 6 | 
                                    
                                    5.7%
                                 | |
| 8 | 7 | 
                                    
                                    6.7%
                                 | |
| 10 | 1 | 
                                    
                                    1%
                                 | |
| 12 | 6 | 
                                    
                                    5.7%
                                 | |
| Sysmiss | 507 |