| Value | Category | 
                                    
                    
                        | -9 | Don't know | 
                                    
                    
                        | -7 | Legal skip | 
                                    
                    
                        | -6 | Unfinished questionnaire | 
                                    
                    
                        | -3 | Interviewer error | 
                                    
                    
                        | 8 |  | 
                                    
                    
                        | 9 |  | 
                                    
                    
                        | 10 |  | 
                                    
                    
                        | 11 |  | 
                                    
                    
                        | 12 |  | 
                                    
                    
                        | 13 |  | 
                                    
                    
                        | 14 |  | 
                                    
                    
                        | 15 |  | 
                                    
                    
                        | 16 |  | 
                                    
                    
                        | 17 |  | 
                                    
                    
                        | 18 |  | 
                                    
                    
                        | 19 |  | 
                                    
                    
                        | 20 |  | 
                                    
                    
                        | 21 |  | 
                                    
                    
                        | 22 |  | 
                            
            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.