By John S. McClenahen Even as signs of an accelerating recovery from the 2001 recession emerge, Merrill Lynch & Co., New York, remains a bit conservative on the U.S. economic outlook. For example, David A. Rosenberg, Merrill's chief North American economist, foresees the economy growing at a 3.75% possibly 4% annual rate this quarter, decidedly under the 5% to 6% rate that some other economists are forecasting. His reasoning: "With the production data still lining up on the soft side, we see a sizable chunk of the spending gains coming from a combination of inventory draw and a leakage to foreign producers (higher imports)." He's also wary of projections of GDP growth near a 4% annual rate in the fourth quarter of this year and the first quarter of 2004. Rosenberg suggests that dramatically less mortgage refinancing activity, higher energy costs and the absence of a hiring spree make the near-4% figure suspect.