September's 20-City Housing Market Index from Case-Shiller showed signs that rapidly rising home prices in some metro areas may be losing momentum. San Francisco, California, posted a month-to-month reading of -0.40 percent and a year-over-year reading of 5.70 percent. Home prices stayed flat in Seattle Washington from August to September, but posted the highest home price gain of 11.00 percent year-over-year. Slowing home price growth in high-demand areas suggest that affordability concerns are impacting rapid gains in home prices seen in recent years.