NEW YORK ( ETF Expert) -- It may not take much to send the markets down these days. A profit miss by Google ( GOOG). A weak revenue showing by McDonalds ( MCD). Or perhaps the most detrimental data point of last week: a 1.7% year-over-year decline in existing-home sales.With interest rates as low as they are, properties have become increasingly affordable. Yet existing homeowners who are marginally underwater may actually become more entrenched; that is, they are less likely to put their homes up for sale when they anticipate additional price gains that could soon make a home-seller's decision profitable. In essence, existing owners will wait until they can exit the "distressed" seller category and enter the normal home-seller segment. Unfortunately, the housing sector cannot fully recover unless the sellers become as active as the buyers; that is, the latter may be excited by rock-bottom rates, but the former are hoping for additional price appreciation that may or may not occur. With its mid-September commitment to purchasing mortgage-backed securities indefinitely ($40 billion per month), the Federal Reserve made it abundantly clear that it ties job growth and economic recovery to a real estate revival. Any hitch in the real estate recovery story seems to severely shake investor faith. In fact, in spite of continued month-over-month momentum in the homebuilder sector, investors have been backing away from the idea that the added Fed stimulus will be a net positive for corporate profitability, sales and/or new hires. Woes at Apple and Google have sent shares of Vanguard Information Technology ( VGT) down sharply over the last month. The producers that pull materials from the earth and send it to big industrial players are not receiving much love either. State Street SPDR Select Sector Industrials ( XLI) as well as iShares DJ Materials ( IYM) have posted negative numbers for the past 30 days as well.