Third-quarter growth revised up to 3.6 percent WASHINGTON (Reuters) - The U.S. economy grew faster than initially estimated in the third quarter as businesses aggressively accumulated stock, but underlying domestic demand remained sluggish. Gross domestic product grew at a 3.6 percent annual rate instead of the 2.8 percent pace reported earlier, the Commerce Department said on Thursday. Economists polled by Reuters had expected output would be revised up to only a 3.0 percent rate. The third-quarter pace is the fastest since the first quarter of 2012 and marked an acceleration from the April-June period's 2.5 percent rate. Businesses accumulated $116.5 billion worth of inventories, the largest increase since the first quarter of 1998. That compared to prior estimates of only $86 billion. Inventories accounted for a massive 1.68 percentage points of the advance made in the July-September quarter, the largest contribution since the fourth quarter of 2011. The contribution from inventories had previously been estimated at 0.8 percentage point. Stripping out inventories, the economy grew at a 1.9 percent rate rather than the 2.0 percent pace estimated last month. A gauge of domestic demand rose at just a 1.8 percent rate. The strong inventory accumulation in the face of a slowdown in domestic demand means businesses will need to draw down on stocks, which will weigh on GDP growth this quarter. Consumer spending, which accounts for more than two-thirds of U.S. economic activity, was revised down to a 1.4 percent rate, the lowest since the fourth quarter of 2009. Spending had previously been estimated to have increased at 1.5 percent pace. Consumer spending grew at a 1.8 percent rate in the April-June period. There were upward revisions to business spending, but estimates for residential construction were lowered. The trade deficit was larger than previously estimated, resulting in trade being neutral to growth in the third quarter.