Year	U.S. dollars (Units)
1980	396.816
1981	300.914
1982	300.392
1983	263.659
1984	270.380
1985	353.788
1986	413.827
1987	187.301
1988	164.966
1989	171.727
1990	271.733
1991	289.247
1992	202.714
1993	200.623
1994	197.895
1995	197.737
1996	252.506
1997	297.228
1998	330.149
1999	364.482
2000	334.841
2001	310.076
2002	317.135
2003	340.566
2004	398.646
2005	432.738
2006	451.128
2007	498.838
2008	579.997
2009	535.666
2010	484.961
2011	604.414
2012	671.212
2013	672.832
2014	683.942
2015	599.400
2016	433.672
2017	463.005
2018	510.380
2019	512.216
2020	456.582
2021	504.038
2022	558.299
2023	629.921
2024	659.095
2025	703.449
2026	724.156
2027	815.223
2028	906.259
2029	975.902