Year	U.S. dollars (Units)
1980	1004.846
1981	1106.193
1982	1031.862
1983	1012.330
1984	1041.933
1985	1059.933
1986	1344.534
1987	1514.218
1988	1493.900
1989	1292.834
1990	1255.123
1991	1357.676
1992	1207.539
1993	1222.984
1994	808.040
1995	745.550
1996	808.211
1997	794.939
1998	772.304
1999	765.544
2000	660.382
2001	687.404
2002	756.140
2003	949.020
2004	1089.418
2005	1101.546
2006	1147.497
2007	1277.667
2008	1439.390
2009	1409.942
2010	1353.407
2011	1464.888
2012	1404.412
2013	1527.773
2014	1604.627
2015	1382.650
2016	1412.866
2017	1468.929
2018	1585.960
2019	1533.161
2020	1539.354
2021	1667.318
2022	1594.592
2023	1711.341
2024	1814.944
2025	1919.991
2026	2010.068
2027	2099.821
2028	2178.160
2029	2263.404