Year	U.S. dollars (Units)
1980	2598.159
1981	3025.972
1982	2219.964
1983	1774.676
1984	1698.949
1985	1434.434
1986	1515.068
1987	1756.210
1988	2035.335
1989	2305.635
1990	2521.569
1991	2849.743
1992	3392.088
1993	3572.096
1994	4058.557
1995	5153.880
1996	5387.405
1997	5799.339
1998	5475.546
1999	4985.768
2000	5099.922
2001	4608.057
2002	4479.771
2003	4824.870
2004	6183.906
2005	7558.009
2006	9410.392
2007	10447.116
2008	10759.738
2009	10176.733
2010	12723.064
2011	14560.249
2012	15316.010
2013	15740.391
2014	14582.850
2015	13494.489
2016	13722.878
2017	15003.770
2018	15755.003
2019	14551.577
2020	13056.638
2021	16037.956
2022	15238.627
2023	16815.783
2024	16616.231
2025	18545.759
2026	19258.396
2027	20009.758
2028	20787.490
2029	21566.944