| Value | Category | 
                                    
                    
                        | 1 | Since birth | 
                                    
                    
                        | 2 | Less than 1 year | 
                                    
                    
                        | 3 | 1 & < 3 Years | 
                                    
                    
                        | 4 | 3 & < 5 Years | 
                                    
                    
                        | 5 | 5 Years or more | 
                                    
                    
                        | 9 | NS | 
                                    
                    
                        | Sysmiss |  | 
                            
            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.