WASHINGTON (MarketWatch) – Business inventories in the U.S. were flat in September following a decline in August, the Commerce Department said Friday. Sales fell 0.2% in the month. The ratio of inventories to sales, meanwhile, was unchanged at 1.40. That’s how many months it would take to sell all the inventory on hand. One year ago, the inventory-to-sales ratio was lower at 1.36. Flat or declining inventories are neutral or subtract from gross domestic product and usually are a sign of a weaker economy. The level of inventories in August was revised down slightly to show a 0.1% decline.