The U.S. economy grew at a tepid 1.7 percent annual rate in the April-June quarter, suggesting growth will stay weak in the second half of the year. Slightly stronger consumer spending and greater exports were the main reasons the Commerce Department reported Wednesday that growth was better than its initial estimate of 1.5 percent. Still, growth has slowed from the 2 percent annual rate in the January-March quarter and the 4.1 percent rate in the fourth quarter of 2011.