Year	U.S. dollars (Units)
1980	2366.797
1981	2691.494
1982	2675.311
1983	2881.660
1984	3202.615
1985	3293.869
1986	4008.134
1987	5325.173
1988	6338.100
1989	7575.906
1990	8167.200
1991	9081.901
1992	10715.536
1993	11256.711
1994	12099.746
1995	13066.128
1996	13588.306
1997	13948.722
1998	12767.078
1999	13752.716
2000	14844.238
2001	13357.195
2002	13651.355
2003	14040.597
2004	15290.307
2005	16427.459
2006	16892.883
2007	17723.704
2008	18053.591
2009	16904.543
2010	19181.358
2011	20838.589
2012	21256.361
2013	21945.460
2014	22844.316
2015	22752.991
2016	23070.733
2017	25061.624
2018	25825.566
2019	25903.168
2020	28571.440
2021	33070.701
2022	32609.595
2023	32443.705
2024	34431.965
2025	36649.723
2026	38602.152
2027	40453.316
2028	41836.924
2029	43103.977