Year	U.S. dollars (Units)
1980	802.627
1981	731.427
1982	712.576
1983	723.654
1984	747.325
1985	817.068
1986	743.735
1987	828.958
1988	875.526
1989	991.295
1990	1062.788
1991	996.472
1992	743.754
1993	522.991
1994	368.840
1995	445.424
1996	555.750
1997	631.280
1998	517.868
1999	474.186
2000	681.129
2001	645.145
2002	872.658
2003	982.806
2004	1254.696
2005	1900.724
2006	2597.964
2007	3121.349
2008	4081.718
2009	3123.699
2010	3586.664
2011	4608.155
2012	5083.827
2013	5228.511
2014	5371.217
2015	4130.930
2016	3468.518
2017	4039.300
2018	3240.858
2019	2612.246
2020	1709.283
2021	2169.648
2022	3439.391
2023	2565.912
2024	2431.580
2025	2444.365
2026	2455.711
2027	2528.702
2028	2571.260
2029	2617.815