Year	U.S. dollars (Units)
1980	123.403
1981	109.806
1982	121.292
1983	126.408
1984	130.117
1985	205.657
1986	241.443
1987	284.263
1988	296.908
1989	253.241
1990	312.102
1991	299.071
1992	351.662
1993	343.493
1994	245.881
1995	333.846
1996	527.121
1997	965.017
1998	777.254
1999	1251.452
2000	1885.985
2001	2616.487
2002	3107.854
2003	5424.130
2004	8214.073
2005	10810.445
2006	12743.347
2007	15782.688
2008	22834.435
2009	16596.742
2010	17153.165
2011	21479.995
2012	21556.417
2013	20252.748
2014	19271.286
2015	11217.985
2016	9202.539
2017	9624.532
2018	9968.089
2019	8355.342
2020	7035.452
2021	8447.959
2022	7853.892
2023	6659.505
2024	6733.327
2025	6558.884
2026	6491.055
2027	6606.787
2028	6656.289
2029	6820.576