Bi-annual US dollars 1987-06-30 7000 1987-12-31 9276 1988-06-30 11964 1988-12-31 13309 1989-06-30 13994 1989-12-31 14301 1990-06-30 16326 1990-12-31 16609 1991-06-30 13381 1991-12-31 13528 1992-06-30 10617 1992-12-31 11199 1993-06-30 19418 1993-12-31 16647 1994-06-30 16858 1994-12-31 13735 1995-06-30 15814 1995-12-31 19037 1996-06-30 16244 1996-12-31 15910 1997-06-30 20519 1997-12-31 18245 1998-06-30 19662 1998-12-31 18733 1999-06-30 10572