ByJohn S. McClenahen Ho! Ho! Ho! This holiday season is likely to be a happy one for retailers. The Conference Board, a New York-based business research group, says the average U.S. household will spend $476 on gifts this year, compared with $455 in 2003, something that could add up to a 4.5% increase in retail sales. Lynn Franco, director of the Conference Board's Consumer Research Center, saw consumers appearing to have more holiday cheer heading into Thanksgiving. Still, some consumers are likely to be spending a lot more than others. For example, households in three Middle Atlantic states (New Jersey, New York and Pennsylvania) will average $550 in holiday spending while households in the Pacific states (Washington, Oregon, California, Alaska and Hawaii) expect to spend an average of $400.