Housing services are a component of personal consumption expenditures (PCE), and consequently part of GDP, in the national income and product accounts (NIPAs). The rental value of tenant-occupied housing and the imputed rental value of owner-occupied housing are both part of PCE housing services, reflecting the amount of money tenants spend for the service of shelter and the amount of money owner occupants would have spent had they been renting. Owner-occupied housing is included in PCE because the NIPAs treat the owner-occupant as if it were a rental business, or in other words, a landlord renting to him or herself. That is, BEA imputes a value for the services of owner-occupied housing (space rent) based on the rents charged for similar tenant-occupied housing, and this value is included in GDP as part of personal consumption expenditures. This imputation is necessary in order for GDP to be invariant when housing units shift between tenant occupancy and owner occupancy.