The US economy grew more slowly than first estimated in the first quarter, at an annual rate of 1.9 percent, the Commerce Department said on Thursday in a new estimate. Growth in gross domestic product, a broad measure of the nation\'s output, was revised downward from last month\'s estimate of 2.2 percent. GDP growth in the world\'s largest economy hit 3.0 percent in the final quarter of 2011. The slower pace in the first three months of the year was largely due to declines in private inventory investment and non-residential fixed investment and a pick-up in imports, the Commerce Department said. It was only a tick below the 2.0 percent pace analysts expected.