U.S. stocks declined on the last trading day of the year, trimming their best annual gain since 2003 after forecasts for warmer weather dragged down energy shares. Exxon Mobil Corp., the world's biggest oil producer, retreated as crude fell below $60 a barrel for the first time in December before recovering. An index of energy shares had the steepest fall the Standard & Poor's 500 Index as the U.S. National Weather Service said temperatures will be higher than normal in most of the country next week. Stocks rose more than Wall Street strategists predicted in 2006 after the Federal Reserve halted two years of interest-rate increases and energy prices fell 22 percent from a July record. The S&P 500 gained 14 percent, the Dow Jones Industrial Average rose 16 percent, and the Nasdaq Composite Index increased 9.5 percent. On average, 15 strategists tracked by Bloomberg News predicted an 8.2 percent rise in the S&P 500. ``It's been a fantastic year,'' said Bill Dwyer, who oversees $12 billion as chief investment officer at MTB Investment Advisors in Baltimore. ``Very few people were forecasting the level of returns we saw. The market proved them wrong.''