| Value | Category | 
                                    
                    
                        | 101 | Weeks: 1 | 
                                    
                    
                        | 199 | Weeks: number missing | 
                                    
                    
                        | 201 | Months: 1 | 
                                    
                    
                        | 299 | Months: number missing | 
                                    
                    
                        | 998 | 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.