| Value | Category | 
                                    
                    
                        | 1 | rarely | 
                                    
                    
                        | 2 | monthly | 
                                    
                    
                        | 3 | weekly | 
                                    
                    
                        | 4 | daily | 
                                    
                    
                        | 6 | not applicable | 
                                    
                    
                        | 8 | not admin. | 
                                    
                    
                        | 9 | missing | 
                                    
                    
                        | 11 | .A | 
                            
            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.