The release this week of the May NZ Property report provided us here at Realestate.co.nz with the opportunity to update one of the key measures of the report – the level of inventory of unsold properties on the market. We have chosen to switch to quoting seasonally adjusted, rather than raw data. This was prompted by review meetings with economists, whose recommendations, I certainly take on board.
However I was approached a couple of times this week to be questioned why we had taken this route when seasonally adjusted data can be seen as “smoothed” or at worst “manipulated”. The view put forward, was that it was best to state the facts and let people make their own assessment. My answer to the question was in some ways supporting and in someways opposing. The NZ Property Report does publish actual data of new listings coming onto the market in the past month as well as actual asking price. The decision to make the inventory stats seasonally adjusted is that it is a calculation, based on actual inventory and actual sales. The issue is that there is a timing factor in the sales data, whereby the two sets of data are out of alignment.This has the potential to distort the inventory statistics.
Reflecting after these questionings I was drawn to want to share some insight behind the differences between actual and seasonally adjusted data. So I have taken the opportunity with the latest Barfoot & Thompson data for May to cast some light on the subject in order to assist greater understanding.
The report from Barfoot & Thompson highlighted the “rise in sale volumes to 792 in May, up on April’s 671 deals but still well behind the year’s peak in March of 927 deals”. These are the actual sales levels, by comparison the seasonally adjusted data shows that May sales were 745, up on April which was 723 and also up on March at 712, in fact the first 5 months of 2010 has seen a steady albeit very slow rise month on month of sales (seasonally adjusted) for Barfoot and Thompson as the largest real estate company in the Auckland region. The chart below shows this particularly well. The critical fact is that by seasonally adjusting the data allows for a true like-for-like comparison between one month and the next.
The calculation of seasonal adjusted sales in this case is made using Barfoot & Thompson own data for the past decade. The inescapable fact is that the property market does move in seasonal cycles through the year, added to the ever present reality that there are different number of days per month which will naturally effect sales numbers.
What is interesting is to look at the seasonal factor for the Barfoot & Thompson data represented in the chart below. Clearly March is traditionally the biggest sales month with nearly 11% of all annual sales whilst December languishes with just 6.5% of sales – in theory an average month would be 8.3%.
Looking at these statistics reinforces the assertion put forward in a prior Unconditional post that Summer may not be the best time to sell a property; because as you see the level of winter activity is pretty consistent, the 5 months through June to October represent a a steady 8.3% average – equal to one twelfth of the annual total.
