Merging Household and individual data are based on matching the identifiers of these two types of data files namely the cluster number (HV001 for the household and V001 for the individual woman or MV001 for the individual men) and the household number ( HV002 for the household, V002 for women, and MV002 for men). In some instances these two variables (cluster number and household number) are not enough to identify the household. In this case using the first 12 characters of the individual identification (CASEID for women or MCASEID for men) would solve the problem. The number of cases will depend on how many individuals would match if you are matching individuals with their corresponding household but no more than the total number of individuals. In case you are matching households with the individual files, this case could lead to a result different from what you are expecting. In case you are merging the person's file with individual data files, the difference between the number of individuals and the persons will be those individuals who don't have a corresponding record in the individual file but the number of records will be no more than the total number of persons in the household.