| Value | Category | 
                                    
                    
                        | 1 | Volunteer | 
                                    
                    
                        | 2 | Paid overtime | 
                                    
                    
                        | 3 | It is part of the work | 
                                    
                    
                        | 4 | Unpaid obligations | 
                                    
                    
                        | 5 | Other | 
                                    
                    
                        | 99 | N/R | 
                                    
                    
                        | 999 | N/A | 
                            
            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.