Year	U.S. dollars (Units)
1980	1007.791
1981	907.551
1982	827.984
1983	800.700
1984	552.842
1985	645.904
1986	484.263
1987	623.605
1988	695.347
1989	701.786
1990	790.827
1991	801.579
1992	830.589
1993	840.415
1994	804.334
1995	815.289
1996	826.192
1997	818.814
1998	815.332
1999	811.257
2000	766.199
2001	737.063
2002	631.566
2003	581.319
2004	642.755
2005	665.721
2006	662.362
2007	780.379
2008	924.514
2009	833.282
2010	860.639
2011	762.761
2012	742.780
2013	700.515
2014	607.429
2015	649.511
2016	683.998
2017	676.656
2018	729.035
2019	768.921
2020	747.886
2021	820.584
2022	841.947
2023	893.223
2024	989.170
2025	1071.564
2026	1116.524
2027	1145.004
2028	1177.299
2029	1230.043