Bi-annual US dollars 1987-06-30 3 1987-12-31 8 1988-06-30 5 1988-12-31 18 1989-06-30 12 1989-12-31 15 1990-06-30 16 1990-12-31 8 1991-06-30 11 1991-12-31 7 1992-06-30 8 1992-12-31 15 1993-06-30 14 1993-12-31 10 1994-06-30 15 1994-12-31 20 1995-06-30 22 1995-12-31 25 1996-06-30 40 1996-12-31 41 1997-06-30 55 1997-12-31 51 1998-06-30 20 1998-12-31 32 1999-06-30 24