Exxon Mobil Corporation on Thursday posted the largest annual profit by a U.S. company-$39.5 billion-even as earnings for the last quarter of 2006 declined 4 percent due to lower natural-gas prices and shrinking profits from gasoline sales. The 2006 profit surpassed Exxon Mobil's own previous record of $36.13 billion set in 2005. Revenue at the world's largest publicly traded oil company rose to $377.64 billion for all of 2006, surpassing the record $370.68 billion the oil giant posted in 2005. “Exxon Mobil continued to leverage its globally diverse resource base to bring additional crude oil and natural gas to market,” company chairman Rex Tillerson said in a statement. Exxon Mobil's record annual earnings followed a year of extraordinarily high energy prices as crude oil topped $78 a barrel in the summer. Prices retreated later in the year. The fourth-quarter decline reflected lower profits from Exxon's refining and marketing operations and a sharp decline in natural-gas prices. In the quarter, Exxon revenue fell 9.4 percent to $90.03 billion. Profit fell to $10.25 billion from $10.71 billion a year earlier. Profits from exploration and production activities were $6.22 billion, down $818 million from a year earlier due to the natural-gas price drop and decreased volumes driven by lower demand in Europe. Profits from refining and marketing operations totaled $1.86 billion, down $430 million due to lower margins. Oil prices in the fourth quarter dropped from the record levels hit in July but were still high, hovering around $60 a barrel. Natural-gas prices, however, were sharply lower than in 2005. Exxon's results for the October-December period were similar to those of U.S. competitor ConocoPhillips, which last week said its fourth-quarter profit fell 13 percent-also because of lower natural-gas prices and refining margins. But strong earnings earlier in the year helped Conoco record its most profitable year on record, earning $15.55 billion in profits.