Bi-annual US dollars 1987-06-30 527 1987-12-31 434 1988-06-30 438 1988-12-31 457 1989-06-30 491 1989-12-31 429 1990-06-30 584 1990-12-31 753 1991-06-30 931 1991-12-31 1085 1992-06-30 1142 1992-12-31 1129 1993-06-30 1358 1993-12-31 1284 1994-06-30 1588 1994-12-31 1809 1995-06-30 2289 1995-12-31 3089 1996-06-30 3053 1996-12-31 3710 1997-06-30 3966 1997-12-31 4358 1998-06-30 1591 1998-12-31 1389 1999-06-30 736