A closely watched index shows home prices dropped by the sharpest annual rate on record in October, but Chicago-area prices didn't fall as much.

The Standard & Poor's/Case-Shiller 20-city housing index released Tuesday fell by a record 18 percent from October last year, the largest drop since its inception in 2000. The 10-city index tumbled 19.1 percent, its biggest decline in its 21 year history.

Chicago-area prices fell 10.8 percent in October compared with October 2007, according to S&P Case/Shiller numbers.