Even as the population of Cook County fell by 141,000 from 2000 to 2007, the number of housing units rose by 75,000. The simple law of supply and demand tells us that housing prices in the county had to have declined as a result. And they have: IAR, Case-Shiller, and my own calculations all show prices of homes for sale have fallen. Rents probably fell as well.
Anyone with even a passing familiarity with urban life knows that changes in rents and house prices vary widely across the county. The supply-demand imbalance would not necessarily affect for-sale and for-rent housing equally. However, it’s not possible to add a net of 75,000 housing units when almost twice that number of people moved away without something giving, and that something was price. (The longer-term trend of lower household sizes could be another explanation, but this chart shows just a decade, and the smaller average household trend happens at a glacial, multi-decade pace.)
You can check out what happened in suburban Lake, Will, Kane, and DuPage counties, as well as the nation as a whole, at Lakeshore Analytics.
Prices of homes for sale are a very widely tracked metric, but there are few, if any, reliable metrics of average rents by neighborhood. (Survey data from the American Community Survey tracks what a person pays in rent, not what an apartment or house costs to rent.) I would guess that this supply-demand imbalance affected the affordability of rents in areas of the county other than the prime neighborhoods.
Jeff Baird is a real estate valuation consultant based in Chicago. He founded Lakeshore Analytics to bring comprehensive, understandable housing data and analysis to Chicago-area readers. The site features a blog with free market news and charts, summary data on 20 top neighborhoods, and quarterly data subscriptions.