| Value | Category | 
                                    
                    
                        | -9 |  | 
                                    
                    
                        | -8 |  | 
                                    
                    
                        | 1 | jan | 
                                    
                    
                        | 2 | feb | 
                                    
                    
                        | 3 | mar | 
                                    
                    
                        | 4 | apr | 
                                    
                    
                        | 5 | may | 
                                    
                    
                        | 6 | jun | 
                                    
                    
                        | 7 | jul | 
                                    
                    
                        | 8 | aug | 
                                    
                    
                        | 9 | sept | 
                                    
                    
                        | 10 | oct | 
                                    
                    
                        | 11 | nov | 
                                    
                    
                        | 12 | dec | 
                                    
                    
                        | 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.