| Value | Category | 
                                    
                    
                        | 1 | Preschool | 
                                    
                    
                        | 2 | Primary | 
                                    
                    
                        | 3 | Secondary | 
                                    
                    
                        | 4 | University | 
                                    
                    
                        | 5 | Post graduate | 
                                    
                    
                        | 6 | Master | 
                                    
                    
                        | 7 | Doctorate | 
                                    
                    
                        | 8 | Don't know | 
                            
            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.