Bi-annual	US dollars
1987-06-30	1658
1987-12-31	1545
1988-06-30	2060
1988-12-31	2208
1989-06-30	1894
1989-12-31	2420
1990-06-30	1969
1990-12-31	1652
1991-06-30	1521
1991-12-31	1505
1992-06-30	1389
1992-12-31	1318
1993-06-30	1523
1993-12-31	1975
1994-06-30	2989
1994-12-31	2087
1995-06-30	2241
1995-12-31	2648
1996-06-30	2576
1996-12-31	2965
1997-06-30	2725
1997-12-31	2889
1998-06-30	2979
1998-12-31	3085
1999-06-30	2015