| Value | 
                    Category | 
                                    
                                                        
                        | 1 | 
                        Great difficulty | 
                                            
                                                        
                        | 2 | 
                        Some difficulty | 
                                            
                                                        
                        | 3 | 
                        A little difficulty | 
                                            
                                                        
                        | 4 | 
                        Fairly easy | 
                                            
                                                        
                        | 5 | 
                        Easy | 
                                            
                                                        
                        | 6 | 
                        Very easy | 
                                            
                                                        
                        | 8 | 
                        DK | 
                                            
                            
            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.