WASHINGTON (MarketWatch) - U.S. retail sales fell 1.2% in September, the biggest drop in three years and the third decline in a row, a further sign that the economy has sunk into a recession led by an exhausted consumer. Retail sales were down 1% compared with a year earlier, the Commerce Department reported Wednesday. Sales were weak in almost all kinds of stores. Excluding the 3.8% drop in auto sales, retail sales fell 0.6%. The 1.2% decline was worse than the 0.8% drop forecast by economists surveyed by MarketWatch.