Year	U.S. dollars (Units)
1980	1342.102
1981	1610.662
1982	1845.826
1983	1827.172
1984	2140.448
1985	2398.651
1986	2838.188
1987	3268.041
1988	3900.915
1989	4377.767
1990	4994.094
1991	4969.991
1992	5447.660
1993	5861.979
1994	6464.269
1995	6874.425
1996	7241.085
1997	8045.301
1998	8276.953
1999	8670.442
2000	9261.826
2001	9963.419
2002	10388.287
2003	10109.465
2004	10882.512
2005	11710.746
2006	13747.809
2007	14660.963
2008	16491.885
2009	16373.910
2010	16427.612
2011	17571.611
2012	17293.961
2013	18315.992
2014	19944.975
2015	20025.807
2016	21079.443
2017	22147.971
2018	22533.727
2019	23205.126
2020	18553.579
2021	18034.852
2022	20423.371
2023	22366.128
2024	23705.137
2025	25187.730
2026	26634.181
2027	27966.676
2028	29313.166
2029	30732.485