| Value | Category | 
                                    
                    
                        | 1 | 1. Preprt roster used | 
                                    
                    
                        | 2 | 2. Preprt rost not used | 
                                    
                    
                        | 3 | 3. No preprint roster | 
                                    
                    
                        | 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.