ByJohn S. McClenahen Higher prices for natural gas, metals and chemicals raised the U.S. Labor Department's import price index a modest 0.2% in November, following a 1.6% increase in October, the largest so far this year. Notably, prices for petroleum imports fell 2.6% last month after increasing a whopping 28.1% during the previous four months. On the other side of the trade ledger, higher export prices for metals, chemicals and other non-agricultural products helped boost the U.S. export price index by 0.3% in November. Prices for agricultural exports fell 0.1% in November, their fifth decline during the last six months.