| Value | Category | Cases | |
|---|---|---|---|
| 0 | no | 1787 | 
                                    
                                    23.4%
                                 | 
| 1 | yes | 3044 | 
                                    
                                    39.9%
                                 | 
| 8 | don't know | 2803 | 
                                    
                                    36.7%
                                 | 
| 11 | .Z | 605 |