Year	U.S. dollars (Units)
1980	1285.181
1981	1202.559
1982	1139.539
1983	1195.617
1984	1094.957
1985	1099.752
1986	1473.694
1987	1852.036
1988	2132.884
1989	2174.940
1990	2590.272
1991	2819.084
1992	3133.035
1993	3191.192
1994	3492.709
1995	3954.762
1996	4047.248
1997	3753.498
1998	3751.708
1999	3911.109
2000	4157.831
2001	4081.162
2002	4252.930
2003	5072.811
2004	5701.753
2005	5590.468
2006	5772.667
2007	6663.186
2008	8138.170
2009	7416.659
2010	8108.095
2011	9320.873
2012	9416.335
2013	9766.770
2014	10366.355
2015	9507.999
2016	9967.673
2017	10844.145
2018	11642.891
2019	11407.849
2020	9010.929
2021	9086.524
2022	10267.027
2023	11396.060
2024	12973.298
2025	13999.562
2026	15034.395
2027	16016.167
2028	17047.711
2029	18124.288