Blue Chip economists trim U.S. growth forecast Sat May 10, 2003 12:00 AM ET WASHINGTON, May 10 (Reuters) - Private economists trimmed their forecasts for U.S. economic growth still further and now regard even the second half of 2003 with pessimism after a slew of data showed the U.S. economy still struggling to recover.The closely watched Blue Chip Economic Indicators newsletter said its panel cut growth forecasts for each of the next three quarters, extending the steady erosion in the survey's outlook that began last summer. Gloomier still, nearly two-thirds of the more than 50 business economists on the panel...