Year	U.S. dollars (Units)
1980	602.924
1981	699.181
1982	778.244
1983	772.741
1984	682.028
1985	596.872
1986	732.197
1987	350.129
1988	324.721
1989	271.496
1990	211.031
1991	237.573
1992	213.148
1993	190.679
1994	195.663
1995	221.366
1996	266.490
1997	307.987
1998	370.188
1999	370.918
2000	380.080
2001	377.469
2002	382.287
2003	401.068
2004	428.911
2005	459.755
2006	491.351
2007	551.847
2008	683.547
2009	700.567
2010	739.903
2011	774.979
2012	867.852
2013	970.271
2014	1030.316
2015	948.688
2016	966.292
2017	1003.776
2018	1001.744
2019	1043.939
2020	1092.613
2021	1137.865
2022	1205.135
2023	1254.229
2024	1220.356
2025	1282.112
2026	1355.058
2027	1446.146
2028	1546.871
2029	1654.152