By John S. McClenahen Mild weather was a factor behind record sales of existing single-family homes in the U.S. in January. But so was consumer confidence. "We have had favorable housing availability conditions for some time, but what's new is the effect of a gradual increase in consumer confidence combined with a turnaround in the economy," says David Lereah, chief economist at the National Assn. of Realtors, Washington, D.C. In January, sales of existing single family homes were at a seasonally adjusted annual rate of 6.04 million, up 16.2% from December 2001's 5.2 million rate. The previous record was an annual rate of 5.49 million units, set in August 2001.