| Value | Category | 
                                    
                    
                        | 1 | Used | 
                                    
                    
                        | 2 | Didn't use | 
                                    
                    
                        | 3 | Used, but didn't pay | 
                                    
                    
                        | 9999998 | REFUSAL | 
                                    
                    
                        | 9999999 | DONTKNOW | 
                                    
                    
                        | Sysmiss |  | 
                            
            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.