Year	U.S. dollars (Units)
1980	15746.262
1981	15484.681
1982	15196.290
1983	14906.174
1984	14968.787
1985	15728.224
1986	18853.038
1987	22445.038
1988	24143.118
1989	24245.515
1990	28187.293
1991	28514.498
1992	30432.890
1993	27880.632
1994	29236.375
1995	34790.001
1996	37225.290
1997	36561.409
1998	34732.137
1999	36300.553
2000	38094.597
2001	38553.843
2002	43083.871
2003	50161.513
2004	57676.821
2005	66924.047
2006	74255.799
2007	85276.992
2008	97119.989
2009	80115.693
2010	87823.805
2011	100815.931
2012	101779.186
2013	103214.973
2014	97302.705
2015	74568.136
2016	70629.250
2017	75940.175
2018	82605.919
2019	76303.683
2020	68275.277
2021	92955.206
2022	108438.547
2023	87739.410
2024	94659.918
2025	99063.714
2026	100171.014
2027	102550.758
2028	104875.665
2029	107586.572