The Dow Jones industrial average rose 117.52 points to close at 16,518.54 after Yellen said the US economy was still in need of support, given“considerable slack” in the labor market.
The Nasdaq slumped, however, after Chinese e-commerce company Alibaba filed initial public offering documents valuing the company below analysts’ expectations.
The Alibaba fililng pushed down shares in Yahoo – which has a 22.6 per cent stake in Alibaba – by 6.6 per cent. Google fell one per cent.
The S&P 500 gained 10.49 points or 0.56 per cent, to end at 1,878.21.
The Nasdaq Composite dropped 13.085 points or 0.32 per cent, to finish at 4,067.673.