Year	U.S. dollars (Units)
1980	275.479
1981	220.336
1982	190.681
1983	180.346
1984	176.396
1985	174.171
1986	237.685
1987	272.304
1988	268.770
1989	322.213
1990	360.285
1991	359.960
1992	362.204
1993	353.655
1994	265.119
1995	336.392
1996	337.183
1997	309.659
1998	313.318
1999	315.484
2000	263.615
2001	299.414
2002	326.736
2003	381.853
2004	427.523
2005	474.257
2006	506.939
2007	579.325
2008	678.346
2009	681.803
2010	688.890
2011	810.040
2012	753.869
2013	778.808
2014	818.665
2015	723.581
2016	749.846
2017	795.387
2018	856.745
2019	840.211
2020	831.034
2021	902.852
2022	827.736
2023	885.880
2024	898.817
2025	923.916
2026	956.634
2027	990.154
2028	1025.229
2029	1060.431