| Value | Category | 
                                    
                    
                        | 1 | no regist. req. | 
                                    
                    
                        | 2 | offic. regis. | 
                                    
                    
                        | 3 | official license | 
                                    
                    
                        | 4 | none present | 
                                    
                    
                        | 5 | D.K. | 
                                    
                    
                        | 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.