Year	U.S. dollars (Units)
1980	13750.491
1981	11429.727
1982	11013.574
1983	10682.307
1984	9904.974
1985	10008.042
1986	13875.191
1987	16895.400
1988	17956.109
1989	17597.260
1990	21581.579
1991	22057.794
1992	24191.955
1993	23356.332
1994	24935.531
1995	29350.802
1996	29084.068
1997	26808.388
1998	28018.706
1999	28393.845
2000	26327.867
2001	26996.172
2002	29401.976
2003	35814.268
2004	40477.300
2005	42054.884
2006	44936.006
2007	51880.384
2008	58015.396
2009	52807.447
2010	51165.823
2011	54342.114
2012	50175.559
2013	52276.986
2014	53026.478
2015	45302.804
2016	46165.177
2017	48799.874
2018	53224.694
2019	52672.504
2020	52222.364
2021	58960.710
2022	57427.756
2023	62718.681
2024	63749.903
2025	65315.916
2026	67444.988
2027	69642.680
2028	71869.919
2029	73990.171