| Value | Category | 
                                    
                    
                        | -9 | Missing | 
                                    
                    
                        | -8 | Don't know | 
                                    
                    
                        | -7 | Notappl | 
                                    
                    
                        | 1 | One week | 
                                    
                    
                        | 2 | Two weeks | 
                                    
                    
                        | 3 | Three weeks | 
                                    
                    
                        | 4 | Four weeks(full month) | 
                                    
                    
                        | Sysmiss |  | 
                            
            Warning: these figures indicate the number of cases found in the data file. They cannot be interpreted as summary statistics of the population of interest.