| Value | Category | Cases | |
|---|---|---|---|
| -998 | Dont know | 0 | 
                                    
                                    0%
                                 | 
| -888 | Other specify | 0 | 
                                    
                                    0%
                                 | 
| 1 | From 9 months to 5 years | 0 | 
                                    
                                    0%
                                 | 
| 2 | Every 6 months | 7 | 
                                    
                                    100%
                                 | 
| Sysmiss | 124 |