| Value | Category | Cases | |
|---|---|---|---|
| 1 | No-no difficulty | 69842 | 
                                    
                                    98.7%
                                 | 
| 2 | Yes-some difficulty | 577 | 
                                    
                                    0.8%
                                 | 
| 3 | Yes- a lot of difficulty | 256 | 
                                    
                                    0.4%
                                 | 
| 4 | can not do at all | 53 | 
                                    
                                    0.1%
                                 | 
| Sysmiss | 11050 |