| Value | Category | 
                                    
                    
                        | -9 | break-off | 
                                    
                    
                        | -7 | Legal skip | 
                                    
                    
                        | -3 | interviewer error | 
                                    
                    
                        | 1 | A certified (formal) apprenticeship | 
                                    
                    
                        | 2 | An informal apprenticeship | 
                                    
                    
                        | 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.