Year	U.S. dollars (Units)
1980	3557.305
1981	4461.156
1982	3162.500
1983	2519.488
1984	2904.686
1985	3015.010
1986	2043.270
1987	2194.692
1988	2631.484
1989	3144.690
1990	3640.260
1991	4281.697
1992	4873.452
1993	5933.292
1994	6086.828
1995	4109.778
1996	4597.153
1997	5484.708
1998	5759.186
1999	6435.620
2000	7467.739
2001	7902.129
2002	7934.694
2003	7390.343
2004	7806.561
2005	8626.151
2006	9456.912
2007	10063.621
2008	10438.499
2009	8346.772
2010	9632.818
2011	10554.350
2012	10631.077
2013	11099.184
2014	11272.395
2015	9915.089
2016	8999.570
2017	9542.783
2018	9970.967
2019	10259.746
2020	8742.217
2021	10180.182
2022	11259.750
2023	13641.613
2024	15248.788
2025	15956.446
2026	16599.542
2027	17221.425
2028	17883.078
2029	18541.892