Bi-annual US dollars 1987-06-30 8 1987-12-31 11 1988-06-30 22 1988-12-31 54 1989-06-30 53 1989-12-31 97 1990-06-30 31 1990-12-31 35 1991-06-30 21 1991-12-31 49 1992-06-30 63 1992-12-31 62 1993-06-30 134 1993-12-31 118 1994-06-30 222 1994-12-31 304 1995-06-30 426 1995-12-31 251 1996-06-30 590 1996-12-31 575 1997-06-30 830 1997-12-31 1167 1998-06-30 1055 1998-12-31 845 1999-06-30 512