Below is a chart of Calgary home sales over the past 5 years from Bob Truman's site and a centered 12 month moving average.
Next is a table of seasonal adjustments for each month. This is done by determining the ratio of actual sales and the centered moving average and taking an average for each month. For example the December ratios are marked below and taking the average we can expect December sales to be 62% of "normal" based on seasonal factors. The method is described in detail here.
January 0.79
February 1.01
March 1.19
April 1.2
May 1.25
June 1.26
July 1.03
August 0.99
September 0.91
October 0.84
November 0.81
December 0.62
This factor is "normalized" and applied to the original sales numbers to get seasonally adjusted sales. Also plotted is a six month moving average.
Finally some benchmarks taken from the marked points on the six month seasonally adjusted sales trend. The first benchmark is the monthly sales at a constant seasonally adjusted rate equivalent to the last six months of 2009. This is described as "It's all good". The second is a sales rate equivalent to the six months of the financial crisis between October 2008 to March 2009. This is described in the following chart as "Scorched earth". The last benchmark is at a seasonally adjusted rate equivalent to that from Nov 2006 to April 2007 called "Back to boom".
I will post the same charts for Edmonton when the official sales numbers are available.*Update*
Radley commented on new listings so I included similar charts to cover that angle. New listings was at least as important to the 2009 recovery as the increase in sales. One of the benchmarks for new listings in 2010 is a seasonally adjusted rate equivalent to the last half of 2009. This represents a relatively low level of new listings and for a market downturn to occur this will need to increase. The other benchmark is the first half of 2008 where sellers were stampeding to the exits.
