Year	U.S. dollars (Units)
1980	5847.707
1981	6454.418
1982	7393.152
1983	6939.437
1984	6831.216
1985	6411.214
1986	4121.173
1987	4085.591
1988	3798.754
1989	3625.717
1990	4221.813
1991	4392.869
1992	4474.142
1993	3743.583
1994	4027.423
1995	4322.255
1996	4658.874
1997	4632.813
1998	4872.619
1999	5479.934
2000	6545.953
2001	7046.379
2002	7162.514
2003	8931.032
2004	10442.168
2005	12471.953
2006	14280.042
2007	16765.857
2008	21448.701
2009	14777.395
2010	16957.433
2011	19300.833
2012	20325.911
2013	21208.309
2014	21799.068
2015	19722.777
2016	17220.758
2017	17369.342
2018	17677.747
2019	17043.863
2020	14868.061
2021	17412.427
2022	21252.661
2023	19801.012
2024	19861.182
2025	20562.165
2026	20845.424
2027	21289.364
2028	21885.524
2029	22476.591