| Value | Category | Cases | |
|---|---|---|---|
| -99 | Don't know | 0 | 
                                    
                                    0%
                                 | 
| -9 | Don't know (spontaneous) | 1 | 
                                    
                                    0.4%
                                 | 
| 0 | 1 | 
                                    
                                    0.4%
                                 | |
| 10 | 3 | 
                                    
                                    1.3%
                                 | |
| 15 | 5 | 
                                    
                                    2.2%
                                 | |
| 20 | 33 | 
                                    
                                    14.7%
                                 | |
| 25 | 52 | 
                                    
                                    23.2%
                                 | |
| 30 | 62 | 
                                    
                                    27.7%
                                 | |
| 35 | 14 | 
                                    
                                    6.3%
                                 | |
| 40 | 13 | 
                                    
                                    5.8%
                                 | |
| 50 | 24 | 
                                    
                                    10.7%
                                 | |
| 60 | 12 | 
                                    
                                    5.4%
                                 | |
| 70 | 2 | 
                                    
                                    0.9%
                                 | |
| 80 | 1 | 
                                    
                                    0.4%
                                 | |
| 100 | 1 | 
                                    
                                    0.4%
                                 | |
| Sysmiss | 136 |