Year	U.S. dollars (Units)
1980	1926.963
1981	1920.127
1982	2006.482
1983	2189.553
1984	2419.501
1985	2154.458
1986	1864.031
1987	2070.009
1988	2213.866
1989	2380.512
1990	2586.278
1991	2885.568
1992	3378.909
1993	3716.921
1994	4029.272
1995	4671.084
1996	5175.901
1997	5012.378
1998	3521.119
1999	3762.769
2000	4347.730
2001	4189.053
2002	4441.824
2003	4740.324
2004	5244.873
2005	5678.332
2006	6351.127
2007	7480.893
2008	8766.175
2009	7543.882
2010	9046.978
2011	10397.902
2012	10806.823
2013	10851.657
2014	11165.249
2015	9663.122
2016	9523.316
2017	9965.123
2018	11079.617
2019	11228.293
2020	10400.219
2021	11475.701
2022	12465.612
2023	12570.460
2024	13314.840
2025	14115.222
2026	14870.382
2027	15556.055
2028	16318.436
2029	17075.157