Year	U.S. dollars (Units)
1980	2329.353
1981	2403.455
1982	2293.938
1983	2280.452
1984	2338.076
1985	2588.553
1986	3165.945
1987	3638.988
1988	4128.118
1989	4407.201
1990	5302.844
1991	5314.655
1992	6128.346
1993	6559.088
1994	6555.429
1995	6748.825
1996	6583.091
1997	7280.929
1998	7715.784
1999	7747.491
2000	7578.829
2001	7663.083
2002	8431.923
2003	8524.935
2004	10176.659
2005	11093.314
2006	12014.418
2007	12155.702
2008	11480.433
2009	9707.265
2010	10805.099
2011	11647.017
2012	11999.897
2013	14762.223
2014	15189.845
2015	15375.608
2016	16721.449
2017	17738.310
2018	18602.985
2019	19366.719
2020	14235.574
2021	15195.623
2022	20804.533
2023	21575.319
2024	21875.075
2025	22973.109
2026	24207.453
2027	25616.316
2028	27139.876
2029	28741.897