The U.S. economy's estimated growth rate in the fourth quarter was slashed to 1.5% from 2.7% by the Atlanta Federal Reserve after declines in retail sales and inventories. The Atlanta Fed was not alone - many Wall Street firms also cut their estimates for gross domestic product after the government reported a 1.2% drop in retail sales in December. The decline was the biggest in nine years. Business inventories also fell in November, adding to the drag on fourth-quarter GDP. Many economists are skeptical about the accuracy of the reported decline in retail sales, but it's a key component of GDP.