Friday, November 23, 2012

Predicting Prices in Vancouver

Below is an overview of an analytical method used to predict Vancouver prices. I have been predicting price changes on a short-term basis (looking out a few months) and this is not done through pie-in-the-sky guesswork, this is based on a defined set of steps and calculations.

Housing-analysis blog creater and owner, and financial planner, "mohican" noticed back in 2007 there was a (negative) correlation between so-called "months of inventory" (MOI), the ratio of reported for-sale inventory to monthly sales, to price changes. MOI tells us how long it will take to clear inventory at current sales rates. Other equivalent measures you may hear are months of supply, sell-list ratio (the inverse of MOI), and months to clear. This blog refers to MOI, and data can be found on REBGV news releases. (Note that Fraser Valley real estate board also published similar stats, and the correlation is good there as well; this analysis is only for REBGV data.)

Price changes are measured using the Teranet HPI, however similar correlations to MOI exist with the MLS-HPI and to a lesser extent median price changes. In order to account for month-month sales noise MOI is averaged over three months. I only have complete monthly inventory data for REBGV to 2005. There are likely data before this but I do not have access to them.

Two further innovations come by first recognizing that correlation changes depending upon the period over which price changes are measured. For example the correlation to quarter-on-quarter price changes is better than month-on-month price changes. Second the correlation becomes better if we time-shift the data (i.e. cross-correlate).

Below is a graph of the cross-correlations between price changes over different intervals and 3-month-moving-average MOI:
What this shows is that the highest correlation exists when correlating half-on-half price changes with a 3 month delay. The scatterplot showing this relationship is below:
Note MOI is displayed on as logarithmic scale. Other correlations are not as good but still not bad. Looking at year-on-year and quarter-on-quarter, both appropriately time-shifted, show the relationship is not as high but still obvious:
The most recent price weakness is shown on the QOQ graph above, indeed 2012 is behaving as previous years.

An important, and powerful, note on these graphs is that because of the time-shifted peak correlation, only MOI numbers from the past are displayed. For example the HOH graph only displays MOI to 3 months ago, the YOY graph only displays MOI to 6 months ago, and the QOQ graph only displays MOI to last month. That means that if we know MOI today (and we do thanks to Realtor Paul Boenisch posting daily sales, listings, and inventory on vancouvercondo.info)  we can use this model to predict prices some months out.

Take the HOH graph above and apply current 3 month average MOI (about 10) to the graph. That implies that we should be seeing a -5% half-on-half change in the Teranet HPI 3 months from now, in January 2013. A weaker measure is to use the YOY graph and forecast prices 6 months from now; based on that measure we should see the Teranet HPI down -4% to -6% year-on-year in April 2013.

In summary a method of forecasting Teranet HPI for Vancouver has been presented. By finding peak negative cross-correlation between months of inventory and price changes over defined periods it is possible to calculate predictions with varying degrees of strength. Further work expanding this method into other cities is possible.

12 comments:

mohican said...

Great work Jesse, I've wanted to expand on the theory for quite some time but life has gotten in the way. You have done a marvellous job.

Ryan M said...

This is why I visit your site. Detailed, rational, and insightful analysis for the public. Thank you for doing us this wonderful service!

jesse said...

Well thank-you Ryan M! I take it one analytical day at a time.

blazespinnaker said...

Impressive work, well done.

Shock Minus Control said...

So, if you believe your model, then you obviously do not think that home prices in Vancouver are going to fall 25-50% like some of your blogging brethren do?

jesse said...

The model states that to get 25-50% price drops it will require either significantly elevated months of inventory or several years of prolonged malaise of similar magnitude to current conditions.

My view, for what it's worth, is that price-rent ratios are elevated by about 70% and potentially more. That will require a reversion in the form of rent increases outpacing price increases. Think of this like a basic market "force equation". The externalities imparting forces on the market is another discussion.

Shock Minus Control said...

I'm pretty skeptical of the price-to-rent ratio as a forecasting tool (based on my own modelling and papers i've read). As a rough valuation guide it has some use, but I really don't think you can make strong quantitative judgements from it, at least not over a useful horizon. Any papers you can recommend to change my mind?

jesse said...

Nope, only as a "price-earnings" valuation metric. If you are convinced WACC is going to be perpetually lower for an extended period perhaps higher valuations are justified. I am seeing better risk-adjusted returns elsewhere.

Unknown said...

Great work! This shed some light on the nature of RE market. If RE market was liquid (or tradeable), this would be a great tool for shorting it.

I also noticed that changes in prices Half-Over-Half is linear with respect to MOI in logarithmic scale. That is interesting on its own as it indicates diminishing effect of MOI on prices.

Elston Marcelo said...

Very good info graphic . It is easy to analyze for a person like me. It helps me to understand about the prediction of housing in Vancouver in 2013 . I've seen different info-graphs in www.calgaryrealestate.pro/ about calgary housing statistics and it is so very easy and useful like this one. Thanks again ..

M- said...

This is a great update to your ongoing technical dissections of the RE market here! Thanks Jesse!

jesse said...

Unknown: "That is interesting on its own as it indicates diminishing effect of MOI on prices"

There may be a couple of reasons for this. First sales and inventory are not independent of each other -- a failure to sell means higher inventory. The relationship therefore contains higher order terms.

Second after inventory reaches a certain amount that is indicative to some degree on the unwillingness of vendors to lower their prices to clear. There are reasons why it is seen better/necessary to keep asking (and desired) prices higher. This would have the effect of leading to a higher number of "unreasonably-priced" properties that aren't really part of the market at all. The US saw this, but had other issues relating to short sales and REO. Canada doesn't appear to have much of this as current.