| Value | Category | 
                                    
                    
                        | 1 | 0-10 books | 
                                    
                    
                        | 2 | 11-25 books | 
                                    
                    
                        | 3 | 26-100 books | 
                                    
                    
                        | 4 | 101-200 books | 
                                    
                    
                        | 5 | more than 200 books | 
                                    
                    
                        | 8 | not admin. | 
                                    
                    
                        | 9 | omitted | 
                                    
                    
                        | 11 | .B | 
                            
            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.