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 24 1994-06-30 25 1994-12-31 22 1995-06-30 21 1995-12-31 22 1996-06-30 37 1996-12-31 22 1997-06-30 42 1997-12-31 20 1998-06-30 25 1998-12-31 28 1999-06-30 9