Normally 53,578 does not equal 84,154 — but in the world of government statistics it does.

A statement from An Phríomh-Oifig Staidrimh, the Central Statistics Office, has suggested that when it wrote that 84,500 new homes had been completed between 2011 and 2017, that in fact meant 53,578.

The reduction in the number of housing completions by slightly more than one-third is the result of a counting error. By relying on the number of new electricity connections — and assuming that meant new houses built — it over-estimated the rate of housebuilding.

Taking 2017 as an example, the CSO said its analysis found that the number of new dwellings was actually 4,825 lower than the number of new electricity connections. Fifty-seven percent of the difference is accounted for by reconnections, 23% by previously completed dwellings in unfinished housing developments and 20% by non-dwelling connection, the statement said.

The CSO believes that in 2017 the number of new dwellings built has increased  to stand at 14,446, a year-on-year increase of 45.7%. In the first quarter of 2018 there were 3,526 new dwellings built.

The housing completions figure is not the only property data set that comes with a health warning.

Newly published figures on the output of the building and construction sector appeared to show an astonishing surge in sector output, up 20.6% in the first quarter of 2018 compared to the last quarter of 2017.

But the data is published with a discrete footnote which said "the CSO will continue to monitor the quality and comparability of this new data series" which means they find the numbers rather surprising.

If the annualised figure is replaced by straight numbers the CSO said the volume of output in building and construction increased by 7.4% in the first quarter when compared with the preceding period.