Year	U.S. dollars (Units)
1980	6128.024
1981	5381.909
1982	5171.535
1983	4501.838
1984	4471.654
1985	4694.759
1986	6477.301
1987	8187.290
1988	9598.667
1989	10566.133
1990	13693.638
1991	14697.501
1992	16013.155
1993	13409.697
1994	13419.620
1995	15475.607
1996	16095.750
1997	14782.949
1998	15457.110
1999	15814.188
2000	14761.108
2001	15400.911
2002	17097.916
2003	21501.074
2004	24932.129
2005	26438.031
2006	28414.133
2007	32588.562
2008	35484.390
2009	32131.382
2010	30566.877
2011	31676.690
2012	28344.913
2013	29094.337
2014	29537.627
2015	25776.217
2016	26549.363
2017	28211.927
2018	30438.338
2019	29603.298
2020	26968.374
2021	30563.552
2022	29799.745
2023	33071.349
2024	34045.166
2025	35072.464
2026	35852.484
2027	36646.005
2028	37526.880
2029	38428.381