WASHINGTON — Officials from six major oil companies have refused to testify this week at a Senate hearing looking into whether oil industry mergers in recent years have made gasoline more expensive at the pump. With oil companies reporting record profits from higher energy prices, consumer groups have complained that mergers in the industry have stifled competition. Exxon Mobil said on Monday it earned $10.7 billion in the fourth quarter of last year and $36.1 billion for all of 2005 — bigger than the economies of 125 countries. The Senate Judiciary Committee, which is holding the hearing on Wednesday morning, said it asked representatives from Exxon Mobil, Chevron, ConocoPhillips, Valero Energy and the U.S. units of BP and Royal Dutch Shell to tell their side of the story. “All declined the invitation to testify,” the committee said in a statement on Monday, without providing details. The companies, with the exception of Valero, took a beating at a Senate hearing last November on the industry’s soaring profits at the time and high energy prices. Bill Kovacic, a member of the Federal Trade Commission, is scheduled to testify at Wednesday’s hearing. The FTC is investigation […]