| Value | Category | 
                                    
                    
                        | 1 | AlotOfDifficulty | 
                                    
                    
                        | 2 | CannotDoAtAll | 
                                    
                    
                        | 3 | NoDifficulty | 
                                    
                    
                        | 4 | SomeDifficulty | 
                                    
                    
                        | Missing value |  | 
                            
            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.