Some 85,154 new houses and apartments were calculated to have been built from 2011 to 2017, but the true number was 53,566 — just 63% of what was believed.
The Central Statistics Office (CSO) uncovered the disparities after being asked by Housing Minister Eoghan Murphy to come up with a more accurate method of counting new builds than the one used by the Government for the last 40 years.
Up to now, governments have relied on electricity connections to tell them how many new homes have been provided — based on the logic that connecting to the grid is one of the last acts before a new dwelling comes ready for occupation.
The CSO found significant over-counting of houses because the electricity connections included reconnections of homes that had been vacant for a period of time, new connections for agricultural buildings that used domestic rather than commercial power supply, and connections to previously completed but unoccupied dwellings in ghost estates.
Under the new method devised by the CSO, electricity connections will still be used in counting new homes but in conjunction with data from sources including the Building Energy Rating programme, Revenue payments such as stamp duty and local property tax, building commencement notices and certificates of compliance, the census of population, and the issuing of Eircodes.
Kieran Culhan, CSO senior statistician, said the resulting figures, although not perfect, were much more reliable than those previously published by the Department of Housing.