By John S. McClenahen For the second time in six weeks, Merrill Lynch & Co. is raising its estimate for operating earnings-per-share (EPS) for the S&P 500. Bruce Steinberg, chief economist at the New York-based securities firm now expects a year-to-year increase of 21% to $47 in S&P 500 operating EPS for 2002. His previous estimate was $45. And looking ahead to 2003, Steinberg forecasts a 19% increase to $56, a dollar more than his earlier estimate of $55. "Productivity and economic growth are even stronger than we previously thought," Steinberg explains. Indeed, Merrill Lynch has just raised its GDP growth forecast for 2002 to an inflation-adjusted 3.2%; it had been 2.6%. What's more, Steinberg figures the accelerated depreciation provision of last month's economic stimulus bill will lower the effective corporate tax rate by about 2.5 percentage points. "That alone adds just over a dollar to the S&P 500 operating EPS this year," he states. In 2001, the S&P operating EPS fell 30%.