| Value | Category | 
                                    
                    
                        | 1 | First quartile | 
                                    
                    
                        | 2 | Second quartile | 
                                    
                    
                        | 3 | Third quartile | 
                                    
                    
                        | 4 | Fourth quartile | 
                                    
                    
                        | 5 | Don't know | 
                                    
                    
                        | 6 | Refused | 
                            
            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.