Senator Saxby Chambliss, a Republican from Georgia, left, talks to Terrence 'Terry' Duffy, chairman and president of CME Group Inc., before a Senate Agriculture Committee hearing in Washington, D.C., U.S., on Tuesday, May 13, 2014. High-speed trading in U.S. futures markets is being dominated by a small number of firms that should be forced to register with regulators to ensure adequate oversight, the Commodity Futures Trading Commission's former chief economist told lawmakers. Photographer: Andrew Harrer/Bloomberg via Getty Images