Vacancy rates are based on the vacancy for properties that are in the NCREIF Property Index (NPI) and thus are a sample of vacancy rates for investment grade real estate. The vacancy rates are averaged for each property that is in the index. Occupancy (the inverse of vacancy) is based tenants that are paying rent for the space and can differ from physical occupancy. The trend in vacancy rates should be considered indicative of the overall trend in vacancy rates for institutional grade real estate income property.