(Reuters) - Economists at Goldman Sachs Group Inc on Monday bumped their U.S. GDP forecast for the second quarter to 11% from 10% and said that additional fiscal measures are likely to be valued at $1.5 trillion, up from their previous $1.1 trillion estimate. On an annual basis, they raised their forecasts for 2021 and 2022 growth by 0.2 percentage points each, to 6.8% and 4.5%, respectively.