Year	U.S. dollars (Units)
1980	1482.823
1981	1390.414
1982	1309.899
1983	1322.840
1984	1286.600
1985	1271.845
1986	1312.226
1987	1382.408
1988	1411.506
1989	1386.015
1990	1716.723
1991	1769.744
1992	2070.007
1993	1903.681
1994	1997.000
1995	2261.968
1996	2411.883
1997	2318.983
1998	2407.491
1999	2505.878
2000	2322.277
2001	2365.245
2002	2460.779
2003	2897.197
2004	3265.224
2005	3350.785
2006	3536.507
2007	3963.791
2008	4519.745
2009	4333.153
2010	4343.057
2011	4471.694
2012	4345.815
2013	4419.705
2014	4511.282
2015	4060.695
2016	3890.127
2017	3656.508
2018	3661.194
2019	3556.377
2020	3573.836
2021	3884.708
2022	3814.405
2023	4191.620
2024	4435.001
2025	4492.333
2026	4637.085
2027	4686.354
2028	4685.984
2029	4702.122