| Value | 
                    Category | 
                                    
                                                        
                        | 0 | 
                        <12 months | 
                                            
                                                        
                        | 1 | 
                        1 year | 
                                            
                                                        
                        | 2 | 
                        2 years | 
                                            
                                                        
                        | 3 | 
                        3 years | 
                                            
                                                        
                        | 4 | 
                        4 years | 
                                            
                                                        
                        | 5 | 
                        5 years | 
                                            
                                                        
                        | 6 | 
                        6+ years | 
                                            
                                                        
                        | 7 | 
                        Non-numeric | 
                                            
                                                        
                        | 8 | 
                        Don't know | 
                                            
                            
            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.