By John S. McClenahen In the current calendar quarter as well as in this year's third and fourth quarters, the U.S. economy is unlikely to match the 5.8% annual rate of inflation-adjusted GDP growth that it posted from January through March. More than half of first-quarter growth was a result of companies restocking their inventories. "The first quarter will likely be the high-water mark for GDP growth this year," says Jerry J. Jasinowski, president of the Washington, D.C.-based National Association of Manufacturers. "Now that the inventory bounce is out of the way and with a modest recovery expected in business investment and exports, slower growth will occur throughout the rest of the year." Even Merrill Lynch & Co., the most bullish of major economic forecasters with a 6% projection for the first quarter, foresees a growth rate no higher than 5% the rest of this year -- and that number not until the fourth quarter. For the current quarter, the New York-based securities firm figures that GDP is growing at a 4% annual rate and it projects a 4.2% annual rate for the third quarter. Consumer spending, which accounts for about two-thirds of the economy, will be a major factor in the amount of actual GDP growth during the rest of this year. Consumer spending rose at a healthy 3.5% rate during the first quarter. However, the University of Michigan's index of consumer sentiment declined to 93 this month from 95.7 in March, suggesting people may do a little more looking than buying in the months ahead. Capital investment also bears close watching. Business investment in equipment and software actually fell at a 0.5% annual rate in the first quarter. "For a sustainable recovery, we need to see stronger growth in investment spending," stresses Thomas J. Duesterberg, president and CEO of the Manufacturers Alliance/MAPI, an Arlington, Va.-based business policy research group. The U.S. Commerce Department's Bureau of Economic Analysis is slated to publish a revised estimate of first-quarter 2002 GDP growth on May 24, when more complete data are likely to be available.