| Value | Category | 
                                    
                    
                        | 1 | Never | 
                                    
                    
                        | 2 | 1-2 times a year | 
                                    
                    
                        | 3 | 3-5 times a year | 
                                    
                    
                        | 4 | Monthly | 
                                    
                    
                        | 5 | More than once a month | 
                                    
                    
                        | 7 | N/A | 
                                    
                    
                        | 8 | Invalid | 
                                    
                    
                        | 9 | Miss | 
                            
            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.