U.K. and Japanese pension funds outperformed plans in the United States last year, according to year-end tallies by leading consultants. Japanese plan sponsors, in fact, ended 1999 with their highest returns in 10 years, said John Stannard, managing director for Frank Russell. The median Japanese pension fund last year saw returns shoot up to 18.3% vs. 1998, when the median fund lost 3.3%. But pension funds in the United Kingdom led the globe, posting a median return of 20% in 1999, up from 14% a year earlier, according to The WM Co. Plan sponsors in the United States, however, saw returns fall flat. The median U.S. fund saw a return of 14.5% last year, down from the 1998 level of 14.7%, according to preliminary data from Callan Associates.