A bevy of solid earnings reports also has lifted investors' optimism. According to FactSet, more than 60% of the companies in the S&P 500 have posted results, with the blended S&P 500 earnings growth rate in the first quarter at 45.8%, up from 24.5% at the start of earnings season and the 15.8% expected at the start of the quarter. About 86% of companies have surpassed analysts' expectations, a record high. Federal Reserve Chairman Jerome Powell said Monday the economic outlook in the U.S. has “clearly brightened” but the recovery has been uneven. The Fed chief said the "economic downturn has not fallen evenly on all Americans and those least able to bear the burden have been the hardest hit.”