By John S. McClenahen A key measure of the U.S. job market declined in July, suggesting that U.S. companies remain cautious about adding workers. The Conference Board's Help-Wanted Advertising Index edged down to 37 last month from 38 in June. "The latest data show essentially no change through July," observes Ken Goldstein, an economist at the New York-based business research group. "Want-ad volume has not changed much over the past six months. Initial unemployment claims reached a plateau in March and have stayed fairly close to that level ever since. Overall economic momentum is no longer firing on all cylinders. And hiring intentions this summer are suggestive that companies may not increase hiring until the economy regains more solid footing." The Conference Board index is based on a monthly survey of help-wanted advertising volume in 51 major newspapers across the U.S.