| Value | Category | 
                                    
                    
                        | -9 | Don't know | 
                                    
                    
                        | -7 | Legal skip | 
                                    
                    
                        | -6 | Unfinished questionnaire | 
                                    
                    
                        | -3 | Interviewer error | 
                                    
                    
                        | 0 |  | 
                                    
                    
                        | 1 |  | 
                            
            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.