| Value | Category | 
                                    
                    
                        | -9 | Don't Know | 
                                    
                    
                        | -8 | Refused | 
                                    
                    
                        | -5 | Not Applicable | 
                                    
                    
                        | -3 | Missing | 
                                    
                    
                        | 1 | Level 1 | 
                                    
                    
                        | 2 | Level 2 | 
                                    
                    
                        | 3 | Level 3 | 
                                    
                    
                        | 4 | Level 4 | 
                                    
                    
                        | 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.