| Value | Category | 
                                    
                    
                        | 1 | Daily | 
                                    
                    
                        | 2 | Weekly | 
                                    
                    
                        | 3 | About once a month | 
                                    
                    
                        | 4 | A few times a year | 
                                    
                    
                        | 5 | Once in the last year | 
                                    
                    
                        | 6 | Not at all in the last year | 
                                    
                    
                        | 7 | Twice a year | 
                                    
                    
                        | 999 | Missing | 
                            
            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.