Year	U.S. dollars (Units)
1980	6381.627
1981	6713.668
1982	7068.390
1983	7719.128
1984	7214.509
1985	6588.298
1986	7986.560
1987	9386.025
1988	11436.536
1989	11439.345
1990	13087.183
1991	13979.058
1992	15080.512
1993	14766.413
1994	16432.305
1995	19002.676
1996	20216.774
1997	20476.932
1998	20169.749
1999	19806.863
2000	21672.162
2001	20916.046
2002	19044.144
2003	19637.118
2004	20554.916
2005	21236.595
2006	22508.534
2007	25649.970
2008	30185.463
2009	28394.840
2010	31350.026
2011	34445.988
2012	33250.574
2013	36945.286
2014	38247.598
2015	36138.714
2016	37568.167
2017	41014.945
2018	42249.336
2019	44155.447
2020	44683.635
2021	52278.239
2022	54967.466
2023	52219.276
2024	53371.545
2025	56205.058
2026	57590.176
2027	59078.862
2028	60726.407
2029	62427.723