| Value | Category | Cases | |
|---|---|---|---|
| -999 | -999 | 4 | 
                                                                 
                                    
                                    2.2%
                                 
                                                             | 
                                                        
                    
| -888 | -888 | 51 | 
                                                                 
                                    
                                    28.2%
                                 
                                                             | 
                                                        
                    
| 1 | More than one month | 9 | 
                                                                 
                                    
                                    5%
                                 
                                                             | 
                                                        
                    
| 2 | Once every month | 10 | 
                                                                 
                                    
                                    5.5%
                                 
                                                             | 
                                                        
                    
| 3 | Once every two months | 9 | 
                                                                 
                                    
                                    5%
                                 
                                                             | 
                                                        
                    
| 4 | Once every three months | 54 | 
                                                                 
                                    
                                    29.8%
                                 
                                                             | 
                                                        
                    
| 5 | Less than once every three months | 44 | 
                                                                 
                                    
                                    24.3%
                                 
                                                             | 
                                                        
                    
| Sysmiss | 731 |