| Value | Category | 
                                    
                    
                        | -9 | Don't Know | 
                                    
                    
                        | -8 | Refused | 
                                    
                    
                        | -5 | Not applicable | 
                                    
                    
                        | -3 | Missing | 
                                    
                    
                        | 1 | A written contract | 
                                    
                    
                        | 2 | A verbal contract | 
                                    
                    
                        | Sysmiss |  | 
                            
            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.