Year	U.S. dollars (Units)
1980	652.593
1981	318.521
1982	414.347
1983	612.565
1984	1044.409
1985	318.956
1986	705.990
1987	856.910
1988	464.581
1989	123.364
1990	121.715
1991	141.111
1992	178.973
1993	234.983
1994	285.953
1995	358.661
1996	419.063
1997	449.338
1998	448.119
1999	465.248
2000	498.579
2001	513.197
2002	546.555
2003	610.357
2004	756.981
2005	873.136
2006	996.255
2007	1152.267
2008	1446.562
2009	1481.442
2010	1628.013
2011	1949.826
2012	2197.619
2013	2369.973
2014	2566.854
2015	2581.907
2016	2720.168
2017	2957.899
2018	3216.254
2019	3439.102
2020	3548.892
2021	3756.885
2022	4101.730
2023	4324.049
2024	4622.544
2025	4977.119
2026	5339.955
2027	5722.016
2028	6123.065
2029	6542.783