| Value | Category | 
                                    
                    
                        | 1 | a | 
                                    
                    
                        | 2 | b | 
                                    
                    
                        | 3 | c | 
                                    
                    
                        | 4 | d | 
                                    
                    
                        | 6 | not reached | 
                                    
                    
                        | 7 | two or more responses, not interpretable | 
                                    
                    
                        | 8 | not admin. | 
                                    
                    
                        | 9 | missing (blank only) | 
                                    
                    
                        | 11 | .B | 
                            
            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.