Bi-annual	US dollars
1987-06-30	9385
1987-12-31	9807
1988-06-30	9438
1988-12-31	8960
1989-06-30	8050
1989-12-31	7505
1990-06-30	7166
1990-12-31	6609
1991-06-30	5940
1991-12-31	6048
1992-06-30	6158
1992-12-31	6108
1993-06-30	5525
1993-12-31	4858
1994-06-30	4745
1994-12-31	4537
1995-06-30	4017
1995-12-31	3979
1996-06-30	3367
1996-12-31	4253
1997-06-30	4898
1997-12-31	3926
1998-06-30	3666
1998-12-31	3697
1999-06-30	2980