The Extraordinary Annual Seasonal Review undertaken this quarter has individually assessed each series to determine how each observation should be treated for estimation of the seasonal factors used to seasonally adjust the current end of the series. This process has ensured disruption to series caused by COVID-19 does not unduly affect estimates of the seasonal factors.
For series which have used the forward factors method (see list below), revisions to the seasonally adjusted series are likely to be larger than the revisions historically observed each quarter when concurrent adjustment was used. Series which have used forward factors have used static seasonal factor estimates since COVID-19 impacts were observed, and the review has updated these seasonal factor estimates. When concurrent adjustment is used, revisions to the seasonally adjusted estimates will typically be smaller because seasonal factor estimates are updated quarterly on the basis of the addition of just one extra data point.
The following Building Activity series previously used the forward factor method:
- Private and total sector non-residential building work done in Victoria (since September 2020 quarter) and Queensland (since March 2021 quarter).
- New houses and alterations and additions to residential commencement series in all states and territories (since December 2020 quarter)
- New houses and alterations and additions to residential work done series in all states and territories (since March 2021 quarter).