| Value | 
                    Category | 
                                    
                                                        
                        | 1 | 
                        Month and year - information complete | 
                                            
                                                        
                        | 5 | 
                        Year - month imputed, age calculated | 
                                            
                                                        
                        | 7 | 
                        Month - date placed | 
                                            
                                                        
                        | 8 | 
                        None - date placed | 
                                            
                                                        
                        | 9 | 
                        From calendar | 
                                            
                            
            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.