Year	U.S. dollars (Units)
1980	12291.741
1981	12496.221
1982	13749.496
1983	14961.600
1984	15630.102
1985	16801.080
1986	17854.136
1987	19329.928
1988	19687.500
1989	21818.620
1990	20460.303
1991	19767.715
1992	19417.216
1993	18979.006
1994	19660.918
1995	20271.249
1996	20974.532
1997	21951.756
1998	23300.816
1999	25780.485
2000	26601.368
2001	26971.273
2002	28357.927
2003	27896.338
2004	28056.572
2005	30030.890
2006	30594.671
2007	31498.523
2008	30787.585
2009	28793.341
2010	28725.135
2011	28365.859
2012	29895.418
2013	28695.885
2014	30055.888
2015	31576.619
2016	31463.129
2017	32471.737
2018	33183.686
2019	33888.774
2020	25049.586
2021	29230.943
2022	32298.948
2023	34224.065
2024	35257.198
2025	36173.394
2026	37053.514
2027	37914.305
2028	38861.507
2029	39829.543