| Value | Category | 
                                    
                    
                        | 1 | 1. Mining industry | 
                                    
                    
                        | 2 | 2. The Military | 
                                    
                    
                        | 3 | 3. Truck driver | 
                                    
                    
                        | 4 | 4. None of the above | 
                            
            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.