| Value | Category | 
                                    
                    
                        | -9 | Don't know | 
                                    
                    
                        | -7 | Legal skip | 
                                    
                    
                        | -6 | Unfinished questionnaire | 
                                    
                    
                        | -3 | Interviewer error | 
                                    
                    
                        | 0 |  | 
                                    
                    
                        | 15 |  | 
                                    
                    
                        | 16 |  | 
                                    
                    
                        | 18 |  | 
                                    
                    
                        | 28 |  | 
                                    
                    
                        | 30 |  | 
                                    
                    
                        | 36 |  | 
                                    
                    
                        | 39 |  | 
                                    
                    
                        | 40 |  | 
                                    
                    
                        | 45 |  | 
                                    
                    
                        | 47 |  | 
                                    
                    
                        | 50 |  | 
                                    
                    
                        | 51 |  | 
                                    
                    
                        | 54 |  | 
                                    
                    
                        | 55 |  | 
                                    
                    
                        | 56 |  | 
                                    
                    
                        | 59 |  | 
                            
            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.