Year	U.S. dollars (Units)
1980	1225.165
1981	969.430
1982	953.628
1983	842.002
1984	752.278
1985	741.673
1986	956.733
1987	1030.894
1988	1193.499
1989	1200.487
1990	1351.480
1991	1418.361
1992	1453.799
1993	1340.916
1994	1482.245
1995	1600.892
1996	1745.452
1997	1561.012
1998	1644.073
1999	1614.860
2000	1486.875
2001	1489.702
2002	1573.475
2003	1914.006
2004	2163.480
2005	2232.944
2006	2427.109
2007	2759.516
2008	3189.200
2009	3162.860
2010	3134.698
2011	3367.347
2012	3224.712
2013	3463.601
2014	3527.712
2015	3235.570
2016	3235.218
2017	3401.256
2018	3615.592
2019	3622.679
2020	3375.435
2021	3905.428
2022	3570.115
2023	3888.585
2024	4077.525
2025	4280.752
2026	4490.390
2027	4692.322
2028	4900.389
2029	5119.350