Year	U.S. dollars (Units)
1980	8361.209
1981	6671.428
1982	3257.853
1983	3962.735
1984	4374.783
1985	3248.745
1986	3857.027
1987	3909.984
1988	4524.498
1989	2867.307
1990	4857.796
1991	6429.454
1992	7653.711
1993	7796.240
1994	8378.735
1995	8295.123
1996	8645.455
1997	9196.516
1998	9283.175
1999	8709.072
2000	8638.543
2001	8085.356
2002	2997.621
2003	3761.088
2004	4314.098
2005	5163.550
2006	5976.082
2007	7315.726
2008	9146.790
2009	8337.811
2010	10412.974
2011	12787.806
2012	13889.792
2013	14488.829
2014	13208.831
2015	14895.316
2016	12772.868
2017	14618.327
2018	11786.433
2019	9941.590
2020	8489.332
2021	10639.378
2022	13640.410
2023	14024.239
2024	12811.840
2025	11733.980
2026	12314.778
2027	12953.291
2028	13517.009
2029	14002.033