The OOHPI is a price index based on the net acquisitions approach, which measures changes in prices faced by owner-occupiers, i.e. households that live in a dwelling that they own. Both owner-occupiers' costs related to acquisition of dwellings and costs related to ownership of dwellings are covered. Item weights are numerical values assigned to each purchase and to associated costs determining their share in the overall house price, rounded to two decimal places. They are updated annually and expressed in per mille.