By BANI SAPRA, AP Business Writer WASHINGTON (AP) — U.S. factory activity shrank in August for the first time since August 2016, a sign that the trade war with China is weighing down a crucial sector of the economy. The Institute for Supply Management, an association of purchasing managers, said Tuesday that its manufacturing index slid to 49.1 last month, from 51.2 in July. Any reading below 50 signals