| Value | Category | 
                                    
                    
                        | 0 | I do not take extra tuition | 
                                    
                    
                        | 1 | No payment | 
                                    
                    
                        | 2 | Money payment | 
                                    
                    
                        | 3 | Another kind of payment | 
                                    
                    
                        | 4 | Both money & kind payment | 
                            
            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.