Chicago Fed factory index drops in October Thursday December 11, 11:59 am ET NEW YORK, Dec 11 (Reuters) - The Chicago Federal Reserve Bank said on Thursday its Midwest manufacturing index fell back in October after a strong rise the month before, but nevertheless the region's factories are on the mend. The Chicago Fed's manufacturing index dropped 1.8 percent to 111.0 in October, after an upwardly revised surge of 3.9 percent in September. Compared with a year ago, the index was down 2.2 percent. Chicago Fed senior economist William Strauss cautioned not to read too much into the October decline,...