| Value | Category | 
                                    
                    
                        | 1 | *100 or more workers | 
                                    
                    
                        | 2 | CE | 
                                    
                    
                        | 3 | Electricity | 
                                    
                    
                        | 4 | Sample  I | 
                                    
                    
                        | 5 | Sample  II | 
                                    
                    
                        | 6 | B & C 100 or more workers | 
                                    
                    
                        | 7 | B&C CE | 
                                    
                    
                        | 8 | B & C Sample I | 
                            
            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.