| Value | Category | 
                                    
                    
                        | 1 | Daily | 
                                    
                    
                        | 2 | Weekly | 
                                    
                    
                        | 3 | Monthly | 
                                    
                    
                        | 4 | Less than monthly | 
                                    
                    
                        | 5 | No regular timing | 
                                    
                    
                        | 98 | Don't know | 
                            
            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.