Year	U.S. dollars (Units)
1980	1203.615
1981	1353.019
1982	1415.339
1983	1110.691
1984	1082.233
1985	1682.789
1986	1913.312
1987	2042.860
1988	2240.525
1989	3021.975
1990	3108.808
1991	2717.508
1992	2561.124
1993	2828.455
1994	3547.020
1995	4923.871
1996	5281.678
1997	5399.969
1998	5199.453
1999	3567.631
2000	3864.917
2001	3256.180
2002	2926.341
2003	3165.195
2004	3750.129
2005	4938.537
2006	6066.958
2007	7572.610
2008	9096.943
2009	8851.059
2010	11578.700
2011	13631.421
2012	12782.844
2013	12752.255
2014	12601.257
2015	9182.996
2016	9117.558
2017	10419.575
2018	9629.603
2019	9364.237
2020	7344.529
2021	8269.709
2022	9612.062
2023	10642.437
2024	11351.871
2025	11808.697
2026	12509.553
2027	13230.253
2028	13847.230
2029	14507.244