| Value | Category | 
                                    
                    
                        | 1 | Primary | 
                                    
                    
                        | 2 | Preparatory | 
                                    
                    
                        | 3 | Secondary | 
                                    
                    
                        | 4 | Above intermediate | 
                                    
                    
                        | 5 | University | 
                                    
                    
                        | 6 | Above university | 
                            
            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.