| Value | Category | 
                                    
                    
                        | 0 | N/A | 
                                    
                    
                        | 1 | higher (university) | 
                                    
                    
                        | 2 | secondary | 
                                    
                    
                        | 3 | primary | 
                                    
                    
                        | 4 | incomplete primary or illiterate | 
                            
            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.