| Value | Category | 
                                    
                    
                        | -4 | missing data | 
                                    
                    
                        | -3 | refused to answer | 
                                    
                    
                        | -2 | not applicable | 
                                    
                    
                        | -1 | do not know | 
                                    
                    
                        | 1 | male | 
                                    
                    
                        | 2 | female | 
                                    
                    
                        | 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.