| Value | Category | 
                                    
                    
                        | 1 | observed, at least 1 valid | 
                                    
                    
                        | 2 | observed , none valid | 
                                    
                    
                        | 3 | reported available, not seen | 
                            
            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.