Year	U.S. dollars (Units)
1980	1380.844
1981	1319.408
1982	1223.390
1983	1194.658
1984	1079.594
1985	975.967
1986	1039.809
1987	1159.833
1988	1565.167
1989	1455.035
1990	1265.882
1991	1444.104
1992	1546.581
1993	1713.713
1994	1834.984
1995	1581.631
1996	1639.773
1997	1527.441
1998	1138.365
1999	1013.232
2000	1007.517
2001	862.099
2002	814.701
2003	995.275
2004	1111.943
2005	1269.526
2006	1411.902
2007	1576.159
2008	1883.527
2009	1833.090
2010	2132.185
2011	2552.043
2012	2865.783
2013	2800.178
2014	2992.711
2015	2742.906
2016	2567.586
2017	2755.488
2018	2861.448
2019	2877.497
2020	2715.968
2021	2216.458
2022	2628.156
2023	2524.633
2024	2530.370
2025	2550.861
2026	2569.773
2027	2599.040
2028	2638.319
2029	2676.699