A household is defined as the residents who, as of 31 December of the year are listed as having the same address in the national register. Residents of institutions or collective living quarters are not included in household statistics. This means that household figures do not represent the total population. An additional requirement for inclusion in a household statistic is that at least one person in the household has been liable to pay tax for the full extent of the year. Individuals aged 18 or over are regarded as adults.