ByJohn S. McClenahen The first official estimate of U.S. GDP growth for the current calendar quarter won't be released by the Commerce Department until July 31. But virtually no one expects it to match the first quarter's "final" figure of 6.1%. "We estimate that GDP [has grown] at a 3.5% in Q2, which, of course, is not exactly weak," says Bruce Steinberg, chief economist at Merrill Lynch & Co., New York. Steinberg figures that means inflation-adjusted GDP has been growing at just over a 4.5% annual rate during the first six months of 2002, a number that the bullish forecaster expects to be repeated during the second half of the year. Meanwhile, for the fourth consecutive week, there are signs the U.S. labor market is stabilizing. Initial claims for unemployment insurance for the week ending June 22 fell to 388,000, a decrease of 10,000 from the previous week's revised figure of 398,000, reports the U.S. Labor Department's Employment & Training Administration. The four-week moving average for claims is now 391,000, down 6,500 from its previous mark. The next major read of the U.S. employment situation is July 5, when the Labor Department is slated to release June data on both payroll employment and joblessness.