| Value | Category | 
                                    
                    
                        | 1 | NO CLASS LIBRARY | 
                                    
                    
                        | 2 | NOT ALLOWED TO BORROW | 
                                    
                    
                        | 3 | ALLOWED TO BORROW | 
                                    
                    
                        | 4 | I DON'T KNOW | 
                                    
                    
                        | 9 | omitted | 
                            
            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.