| Value | 
                    Category | 
                                                                            
                                    
                    
                        | 1 | 
                        Less than 1 year  | 
                        
                            
                        
                        
                        
                        
                            
                    
                                    
                    
                        | 2 | 
                        1 to 4 years  | 
                        
                            
                        
                        
                        
                        
                            
                    
                                    
                    
                        | 3 | 
                        5 to 9 years  | 
                        
                            
                        
                        
                        
                        
                            
                    
                                    
                    
                        | 4 | 
                        10 or more years  | 
                        
                            
                        
                        
                        
                        
                            
                    
                                    
                    
                        | 8 | 
                        Unknown  | 
                        
                            
                        
                        
                        
                        
                            
                    
                                    
                    
                        | 9 | 
                        NIU (not in universe)  | 
                        
                            
                        
                        
                        
                        
                            
                    
                            
            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.