A key measure of U.S. manufacturing activity rose more than expected in September. The MNI Chicago Report clocked in a solidly expansionary 55.7, up from 53 in August. Any reading greater than 50 indicates expansion. Looking ahead, "we're assuming a strong fourth quarter as assembly rates keep rising. ... I think you've got a nice floor for the factory sector into year-end," said Mike Englund, chief economist of Action Economics in Boulder, Colo.