Senator Barack Obama (D-IL) (R) stands in front of Senator Hillary Clinton (D-NY) as they arrive for U.S. President George W. Bush's annual State of the Union speech to a joint session of Congress at the U.S. Capitol in Washington in this January 23, 2007 file photo. Hillary Clinton announced her second run for the presidency on April 12, 2015 starting her campaign as the Democrats' best hope of fending off a crowded field of lesser-known Republican rivals and retaining the White House. (Photo by Larry Downing/Reuters)

A humanoid robot named Kansei, meaning “sensibility” in Japanese, makes a facial expression depicting “happiness”, next to the word “Love” during a demonstration at a laboratory of Meiji University's Robot and Science Institute in Kawasaki, south of Tokyo in this June 4, 2007 file photo. Three-fourths of robot installations over the next decade are expected to be concentrated in four areas: transportation equipment, including the automotive sector; computer and electronic products; electrical equipment and machinery. Labor costs have climbed in countries such as China that have been popular for outsourcing production, while technological advances for robots allow them to be more flexible and perform more tasks. (Photo by Yuriko Nakao/Reuters)

A trader speaks on the phone at his desk at the Frankfurt stock exchange, Germany, in this June 29, 2015 file photo. Federal Reserve policymakers are widely seen raising interest rates for the first time in almost a decade at their next meeting this week. (Photo by Ralph Orlowski/Reuters)

Anissa Barbato from New York looks out over the city as she takes pictures from the Edge, the highest outdoor sky deck in the Western Hemisphere on September 2, 2020 as it reopened to the public in New York. Rising 1,131 feet in the air from the heart of Hudson Yards it offers 360-degree views of New York Citys iconic skyline from the 100th floor outdoor viewing. (Photo by Timothy A. Clary/AFP Photo)

A Japanese white-eye is seen on a branch of cherry blossoms at Kyoto Imperial Palace on March 26, 2010 in Kyoto, Japan. (Photo by Akihiro I/Getty Images)

A member of the Eton public school O.T.C. (Officers Training Corps) practising shouting out orders during a training session, 20th January 1940. (Photo by Hulton Archive/Getty Images)

A protester uses molotov cocktails against riot police during May Day protests on May 1, 2010 in Athens, Greece. (Photo by Milos Bicanski /Getty Images)

A window cleaner passes a lighter to his colleague while rappelling from a new building in Tianjin March 23, 2007. (Photo by Reuters/Stringer)