| Value | Category | 
                                    
                    
                        | 1 | never | 
                                    
                    
                        | 2 | several times a year | 
                                    
                    
                        | 3 | 2 - 3 times a month | 
                                    
                    
                        | 4 | once a week | 
                                    
                    
                        | 5 | 2 - 3 times a week | 
                                    
                    
                        | 6 | every day | 
                            
            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.