Year	U.S. dollars (Units)
1980	10734.896
1981	10439.364
1982	9936.331
1983	9463.110
1984	8951.397
1985	9498.885
1986	11555.907
1987	14331.774
1988	17388.880
1989	17653.750
1990	20913.040
1991	21738.274
1992	22394.494
1993	20015.280
1994	21460.020
1995	23171.120
1996	24432.614
1997	26772.972
1998	28283.064
1999	28768.448
2000	28337.638
2001	27916.906
2002	30127.493
2003	34480.168
2004	40410.653
2005	42143.874
2006	44589.681
2007	50419.848
2008	47884.160
2009	38892.333
2010	39641.869
2011	42106.640
2012	42501.709
2013	43469.644
2014	47468.211
2015	44978.619
2016	41114.514
2017	40617.562
2018	43275.096
2019	42712.614
2020	40245.884
2021	46704.465
2022	45730.102
2023	49098.977
2024	51074.793
2025	53627.266
2026	56759.134
2027	59870.371
2028	63279.415
2029	66911.100