| Value | Category | 
                                    
                    
                        | 1 | Every day | 
                                    
                    
                        | 2 | At last once a week | 
                                    
                    
                        | 3 | At least once a month | 
                                    
                    
                        | 4 | At least every 2-3 months | 
                                    
                    
                        | 5 | Rarely or never | 
                                    
                    
                        | 6 | Don't know | 
                                    
                    
                        | 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.