| Value | Category | 
                                    
                    
                        | -99 | Refused to answer | 
                                    
                    
                        | -88 | Not provided | 
                                    
                    
                        | -77 | Not applicable | 
                                    
                    
                        | -66 | Do not know | 
                                    
                    
                        | -44 |  | 
                                    
                    
                        | 1 | Land | 
                                    
                    
                        | 2 | Airport | 
                                    
                    
                        | 3 | Sea | 
                                    
                    
                        | 4 | River/Inland lake | 
                                    
                    
                        | 5 | Other | 
                            
            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.