| Value | Category | 
                                    
                    
                        | 0 | Never | 
                                    
                    
                        | 1 | Sometimes/occasionally/only once | 
                                    
                    
                        | 2 | Often/frequently | 
                                    
                    
                        | 9 | Don't know | 
                                    
                    
                        | 98 | Refused | 
                                    
                    
                        | 99 | Missing data | 
                            
            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.