Federal Reserve Board Chair Janet Yellen testifies during a hearing before the Senate Banking, Housing and Urban Affairs Committee February 24, 2015 on Capitol Hill in Washington, DC. (Alex Wong/Getty Images)
Investors watch a digital screen displaying the prices of China's stock market on January 5, 2015 in Hangzhou, Zhejiang province of China. (ChinaFotoPress via Getty Images)
A flame from a Saudi Aramco oil installation in the Saudi Arabian desert near the oil-rich area Al-Khurais, 160 kms east of the capital Riyadh, on June 23, 2008. (MARWAN NAAMANI/AFP/Getty Images)
Chinese Education Minister Yuan Guiren at a signing ceremony during German-Chinese government consultations on October 10, 2014 in Berlin, Germany. (Adam Berry/Getty Images)