NEW YORK (CNNMoney.com) -- Over the next few years, more than three-quarters of the nation's housing markets will suffer a decline in home prices. Many will experience double-digit hits in a forecast that has worsened considerably in recent months. According to an analysis conducted by Moody's Economy.com, price declines will exceed 10 percent in 86 of the 379 largest housing markets. And 290 of the cities will experience price drops of 1 percent or more. All are median prices for single-family houses. Nationally, Moody's is projecting an average price decline of 7.7 percent. That's a jump from the 6.6 percent...