Case-Shiller: Spring Slow to Arrive in Boston as Home Prices Slip

It’s time for our monthly check-in of the S&P/Case-Shiller Home Price Indices (HPI). The Case-Shiller data is generally considered to be the most reliable measure of overall home price changes for a region, since they only consider repeat sales of homes when calculating their index, instead of looking at all the homes that sold in a given month.

For the full source data behind this post, hit the S&P/Case-Shiller website. For a more detailed explanation of how the Case-Shiller Home Price Index is calculated, check out their methodology pdf. Also remember that the data released on the last Tuesday of a given month is for the period two months prior (i.e. – April data is released in June).

Here are the basic Case-Shiller stats for the Boston area* as of April:

April 2011
Month to Month: Down 0.2%
Year to Year: Down 4.2%
Prices at this level in: January 2003
Peak month: September 2005
Change from Peak: Down 19.4% in 67 months
Low Tier: Under $248,665
Mid Tier: $248,665 to $382,060
Hi Tier: Over $382,060

Only seven of the twenty metro areas tracked by Case-Shiller saw a decrease in their HPI between March and April (down from eighteen the previous month). The biggest increase was in Washington DC again with a solid 3.0% gain. Other markets that saw increases above 1% were San Francisco (+1.7%), Atlanta (+1.6%), Seattle (+1.6%), Denver (+1.5%), and Cleveland (+1.2%).

Here’s a look at the latest local tiered data, back through 2000:


And here’s a closer look at the recent changes, with the vertical and horizontal axes zoomed in to show just the last year:


Although the middle tiers gained a bit of ground this month, Boston’s low tier and high tier continued to slip. Month to month, the low tier was down 4.1%, the middle tier rose 1.6%, and the high tier decreased 0.3%.

Here’s a chart of Case-Shiller HPIs for all the markets that Redfin serves:


Here’s our peak decline chart, in which we line up the peak Case-Shiller HPI value for each of Redfin’s markets, so we can see how long each market has been declining, and how much it has dropped from the peak.


Six of the twenty cities tracked by Case-Shiller hit another new post-peak low as of April, but the 20-city composite ticked up slightly from its March post-peak low.

Methodology: The Case-Shiller index tracks price changes in sets of homes of similar size and style to better determine changes in what people are willing to pay for the same home over time. If data is available from an earlier transaction for the same home, the two sales are paired and treated as a “repeat sale.” Repeat sales that are too far apart, sales between family members, lot splits, remodels, and property type changes (e.g. from single-family to condos) are excluded from the calculations. All remaining repeat sales are totaled together and weighted based on the time between each sale, then the data for the most recent three months is averaged together to create a given month’s index value (i.e. – September’s index represents the average of the data from July through September).

The three price tiers plotted in the charts below simply represent the top, middle, and bottom third of all sales, based on the initial sale price. In other words, if there were 3,000 sales in the three-month period, 1,000 of them would be in the low tier, 1,000 in the middle tier, and 1,000 in the high tier, by definition.

*[Case-Shiller defines Boston as the entire Boston-Cambridge-Quincy, MA-NH Metropolitan Statistical Area, which includes all or part of the following counties: Essex MA, Middlesex MA, Norfolk MA, Plymouth MA, Suffolk MA, Rockingham NH, and Strafford NH.]