Year	U.S. dollars (Units)
1980	2730.694
1981	2301.277
1982	2422.242
1983	1891.283
1984	1221.720
1985	1080.898
1986	1174.016
1987	1075.998
1988	1206.847
1989	1188.851
1990	1192.380
1991	1120.914
1992	973.197
1993	1222.443
1994	639.608
1995	601.803
1996	750.736
1997	642.729
1998	461.123
1999	410.453
2000	397.025
2001	146.542
2002	171.076
2003	171.505
2004	189.173
2005	226.776
2006	265.901
2007	310.819
2008	366.699
2009	291.745
2010	338.802
2011	387.825
2012	427.848
2013	481.137
2014	512.244
2015	519.680
2016	477.259
2017	478.789
2018	564.342
2019	578.891
2020	546.430
2021	620.605
2022	681.055
2023	673.033
2024	714.763
2025	779.729
2026	835.574
2027	899.209
2028	954.074
2029	1010.148