Forbes reports another indicator in the slow rebound of the housing market is in California, where in January, 31 percent of all real estate transactions were in cash, up by more than double the 14 percent historical average.  The article quotes First Tuesday as saying the tight credit market is the reason, and it is especially true for the more modest homes.  A cash offer may reduce the price by 10 percent.  Tighter credit may push home prices down even further.