Year	U.S. dollars (Units)
1980	8496.811
1981	7693.059
1982	7596.908
1983	7878.146
1984	7783.391
1985	8034.389
1986	11377.320
1987	14280.593
1988	15817.576
1989	16439.473
1990	20500.667
1991	21636.193
1992	22947.484
1993	18437.044
1994	19009.467
1995	20675.320
1996	23094.382
1997	21858.450
1998	22348.051
1999	22029.702
2000	20153.083
2001	20505.923
2002	22386.262
2003	27580.477
2004	31342.833
2005	32031.448
2006	33448.063
2007	37828.364
2008	40818.960
2009	36982.806
2010	35815.593
2011	38276.057
2012	34743.751
2013	35534.990
2014	35836.183
2015	30463.696
2016	31190.794
2017	32648.756
2018	34917.563
2019	33628.161
2020	31788.997
2021	36401.883
2022	35043.092
2023	38325.839
2024	39579.560
2025	40700.723
2026	41611.852
2027	42604.231
2028	43834.553
2029	45095.652