| Value | Category | 
                                    
                    
                        |  | No obstacle | 
                                    
                    
                        | 1 | Minor obstacle | 
                                    
                    
                        | 2 | Moderate obstacle | 
                                    
                    
                        | 3 | Major obstacle | 
                                    
                    
                        | 4 | Very severe obstacle | 
                            
            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.