WASHINGTON - U.S. wholesale inventories surged in December for a second straight month, as previously reported, and sales recorded their biggest increase since 2011, signs of confidence in the economy amid strengthening domestic demand. The Commerce Department said on Thursday that wholesale inventories increased 1.0 percent after a similar jump in November. The back-to-back strong increases of stock accumulation, however, suggest a moderation in the pace of inventory investment in the months ahead. The department reported last month that wholesale inventories rose 1.0 percent in December. The component of wholesale inventories that goes into the calculation of gross domestic product - wholesale stocks excluding autos - increased 0.9 percent in December. Inventory investment contributed one percentage point to the economy's 1.9 percent annualized growth rate in the fourth quarter. That was the second straight quarterly contribution to GDP growth.