Year	U.S. dollars (Units)
1980	1214.379
1981	1310.503
1982	1479.509
1983	1289.230
1984	948.000
1985	878.359
1986	1034.771
1987	1158.596
1988	1372.734
1989	1588.557
1990	1971.695
1991	1799.773
1992	1804.411
1993	2249.320
1994	2234.803
1995	2660.153
1996	2975.134
1997	3347.367
1998	3467.544
1999	3473.435
2000	3510.575
2001	3529.711
2002	3709.572
2003	3586.441
2004	3855.674
2005	4241.399
2006	4494.630
2007	4829.296
2008	5134.246
2009	4507.186
2010	4894.369
2011	5332.520
2012	5448.456
2013	5238.147
2014	5105.511
2015	5204.825
2016	5183.462
2017	5413.030
2018	5729.757
2019	5781.785
2020	5072.599
2021	5354.830
2022	6197.798
2023	6875.672
2024	7309.314
2025	7576.182
2026	7817.250
2027	8066.262
2028	8325.393
2029	8592.950