By MARTIN CRUTSINGERWASHINGTON (AP) â¿¿ A measure of the U.S. economy designed to signal future activity increased in December from November, suggesting growth may strengthen in early 2013. The Conference Board said Thursday that its index of leading indicators rose 0.5 percent in December, the best showing since September. In November, the index was unchanged. The gauge is designed to anticipate economic conditions three to six months out. A decline in applications for unemployment benefits, gains on Wall Street and increases in applications for building permits drove the index higher in December. Conference Board economist Kenneth Goldstein said the rebound in the leading index suggested an improving outlook in contrast to a few months ago when the expectations were not so optimistic. "Housing, which has long been a drag, has turned into a positive for growth, and will help improve consumer balance sheets and strengthen consumption," Goldstein said. "However, for growth to gain more traction we also need to see better performance on new orders and an acceleration in capital spending." Five of the 10 indicators that make up the index were positive factors in December. Consumers' dim outlook for business conditions and weaker expectations for manufacturing orders held back the index. The index is derived from data that for the most part have already been reported individually. On Thursday, the Labor Department said weekly applications for unemployment claims continued to trend lower. The fell last week to a seasonally adjusted 330,000, a five-year low. Home builders started work in 2012 on the most new homes in four years, the Commerce Department said last week. And stock prices are rising even faster in January than last month. The Standard & Poor's 500 index on Thursday briefly traded above 1,500 on Thursday, the first time that has happened since December 2007.