Year	U.S. dollars (Units)
1980	4507.150
1981	4940.784
1982	5146.929
1983	5257.186
1984	5777.438
1985	6058.641
1986	6495.499
1987	6987.398
1988	7579.339
1989	8094.290
1990	8675.576
1991	9093.480
1992	9687.443
1993	10255.532
1994	10942.949
1995	11667.589
1996	12305.024
1997	12968.394
1998	14430.159
1999	15293.182
2000	16192.127
2001	18243.709
2002	18972.770
2003	19820.208
2004	20988.989
2005	21959.317
2006	22935.951
2007	23664.874
2008	24898.335
2009	25768.726
2010	26435.742
2011	27278.853
2012	27944.742
2013	28513.150
2014	28981.343
2015	29755.350
2016	30585.550
2017	31347.273
2018	31549.375
2019	32851.875
2020	32643.179
2021	33240.313
2022	35448.438
2023	36369.133
2024	37171.719
2025	38203.077
2026	39415.171
2027	41312.057
2028	42902.328
2029	44476.892