| Value | Category | 
                                    
                    
                        | 1 | Month and year | 
                                    
                    
                        | 3 | Year -var=missing/DK | 
                                    
                    
                        | 5 | Month-var=missing/DK | 
                                    
                    
                        | 6 | None -var=missing/DK | 
                            
            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.