| Value | Category | 
                                    
                    
                        | 1 | household selected at random, not surveyed in analogous months of the previous years and not exchanged in a given month | 
                                    
                    
                        | 2 | household surveyed in analogous month of the previous year and not exchanged in a given month | 
                                    
                    
                        | 3 | household surveyed in analogous months of two previous years and not exchanged in a given month | 
                                    
                    
                        | 4 | household surveyed in analogous months of three previous years and not exchanged in a given month | 
                                    
                    
                        | 5 | household surveyed in analogous month of the previous year (previous years) and not exchanged in a given month | 
                                    
                    
                        | 6 | household surveyed in analogous month of the previous year (previous years) and discontinued survey within the month | 
                                    
                    
                        | 7 | household selected at random not surveyed in analogous months of the previous years and exchanged in a given month | 
                                    
                    
                        | 8 | household selected at random not surveyed in analogous months of the previous years and discontinued survey within the month | 
                                    
                    
                        | 9 | household selected from the computer list and not exchanged in the given month | 
                                    
                    
                        | 10 | household selected from the computer list and exchanged in the given month | 
                                    
                    
                        | 11 | household selected from the computer list and discontinued examination in the given month | 
                            
            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.