ByJohn S. McClenahen Toss another shrimp on the Barbie to mark another monthly increase for the index of leading economic indicators for Australia. The index increased 0.3% this past March, the latest month for which data are available, and has now grown at about a 5.5% annual rate since mid-2003, reports the Conference Board, a New York-based business research group. The leading index for Australia now stands at 153.1 (1990=100). "The continued strength in the leading index suggests that relatively strong economic growth is likely to persist in the near term," says the Conference Board.