| Value | Category | 
                                    
                    
                        | 1 | Once a week | 
                                    
                    
                        | 2 | Once a month | 
                                    
                    
                        | 3 | Once a couple of months | 
                                    
                    
                        | 4 | About twice a year | 
                                    
                    
                        | 5 | Once a year | 
                                    
                    
                        | 6 | Other | 
                                    
                    
                        | 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.