Year	U.S. dollars (Units)
1980	1595.047
1981	1497.841
1982	1803.464
1983	2056.958
1984	2042.040
1985	1899.817
1986	1965.541
1987	1691.129
1988	1819.392
1989	1772.091
1990	1629.047
1991	2105.486
1992	2315.647
1993	2351.742
1994	2692.704
1995	3612.264
1996	4066.179
1997	4075.977
1998	4459.097
1999	4348.147
2000	4485.064
2001	4987.859
2002	5205.517
2003	5699.557
2004	6684.675
2005	8023.921
2006	9031.797
2007	11252.863
2008	13999.496
2009	11532.283
2010	12510.805
2011	13776.572
2012	13010.540
2013	13550.385
2014	14183.116
2015	12545.188
2016	12369.893
2017	13819.834
2018	15504.366
2019	15694.594
2020	15792.610
2021	18008.152
2022	18278.144
2023	21995.995
2024	23013.882
2025	24143.698
2026	25646.252
2027	26976.259
2028	28087.029
2029	29259.126