Bi-annual US dollars 1987-06-30 0 1987-12-31 0 1988-06-30 0 1988-12-31 0 1989-06-30 0 1989-12-31 0 1990-06-30 0 1990-12-31 0 1991-06-30 0 1991-12-31 0 1992-06-30 0 1992-12-31 0 1993-06-30 0 1993-12-31 21 1994-06-30 19 1994-12-31 34 1995-06-30 45 1995-12-31 40 1996-06-30 45 1996-12-31 55 1997-06-30 37 1997-12-31 46 1998-06-30 43 1998-12-31 38 1999-06-30 22