Year	U.S. dollars (Units)
1980	767.972
1981	677.895
1982	645.372
1983	559.501
1984	529.936
1985	563.251
1986	773.090
1987	902.228
1988	865.668
1989	828.149
1990	936.148
1991	894.485
1992	930.568
1993	852.610
1994	560.956
1995	693.418
1996	706.864
1997	642.569
1998	686.369
1999	689.683
2000	614.004
2001	648.446
2002	680.830
2003	831.623
2004	931.745
2005	993.237
2006	1027.786
2007	1197.551
2008	1403.795
2009	1307.516
2010	1272.622
2011	1366.534
2012	1318.614
2013	1372.686
2014	1397.017
2015	1219.373
2016	1269.553
2017	1361.221
2018	1458.730
2019	1436.224
2020	1465.244
2021	1603.346
2022	1569.546
2023	1729.274
2024	1899.731
2025	2084.308
2026	2179.998
2027	2266.308
2028	2395.366
2029	2481.079