Paris, May 16 (BridgeNews) - The U.S. economy will probably continue to grow at an unacceptably slow rate in the second and third quarters, but it will start to pick up in the fourth quarter amid the lagged effects of monetary stimulus by the Federal Reserve and a flow of cash back to consumer's pockets from the Bush administration's tax cuts, Glenn Hubbard, the newly-appointed chairman of the U.S. Council of Economic Advisors, said.