Year	U.S. dollars (Units)
1980	855.471
1981	776.778
1982	721.655
1983	644.505
1984	646.568
1985	622.803
1986	716.685
1987	758.168
1988	759.500
1989	728.334
1990	737.217
1991	674.688
1992	644.604
1993	434.817
1994	505.909
1995	623.714
1996	686.847
1997	677.772
1998	742.089
1999	647.889
2000	617.147
2001	617.055
2002	611.901
2003	668.483
2004	692.718
2005	778.333
2006	854.992
2007	1028.239
2008	1118.769
2009	1123.268
2010	1176.311
2011	1178.599
2012	1396.220
2013	1490.422
2014	1613.101
2015	1625.176
2016	1688.852
2017	1805.398
2018	1987.302
2019	2107.735
2020	2067.987
2021	2208.691
2022	2245.284
2023	2113.407
2024	1983.099
2025	2055.065
2026	2175.193
2027	2287.204
2028	2414.570
2029	2548.576