Bi-annual US dollars 1987-06-30 2 1987-12-31 23 1988-06-30 12 1988-12-31 7 1989-06-30 3 1989-12-31 2 1990-06-30 2 1990-12-31 4 1991-06-30 3 1991-12-31 2 1992-06-30 8 1992-12-31 0 1993-06-30 44 1993-12-31 58 1994-06-30 69 1994-12-31 84 1995-06-30 130 1995-12-31 144 1996-06-30 197 1996-12-31 235 1997-06-30 233 1997-12-31 293 1998-06-30 297 1998-12-31 319 1999-06-30 304