| Value | Category | 
                                    
                    
                        | 1 | Not iodized 0 PPM | 
                                    
                    
                        | 2 | Less than 15 PPM | 
                                    
                    
                        | 3 | 15 PPM or more | 
                                    
                    
                        | 7 | Missing | 
                                    
                    
                        | 8 | No salt in home | 
                                    
                    
                        | 9 | Salt not tested | 
                                    
                    
                        | 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.