Year	U.S. dollars (Units)
1980	41311.881
1981	42237.276
1982	36927.264
1983	32717.479
1984	29957.847
1985	27912.523
1986	21198.712
1987	22345.786
1988	19032.876
1989	21142.453
1990	27484.598
1991	25577.028
1992	25833.806
1993	25033.005
1994	25737.492
1995	26309.298
1996	29821.120
1997	29909.645
1998	26571.562
1999	27833.669
2000	34386.178
2001	32621.364
2002	32790.740
2003	35017.316
2004	39301.136
2005	43983.848
2006	44313.566
2007	41466.918
2008	39073.380
2009	30920.369
2010	36324.592
2011	42986.879
2012	45108.027
2013	46207.448
2014	47063.628
2015	41422.602
2016	40483.337
2017	41971.753
2018	45591.680
2019	43981.605
2020	37648.963
2021	43438.523
2022	52625.126
2023	51908.699
2024	53916.025
2025	55781.488
2026	58139.358
2027	60895.294
2028	64038.482
2029	67538.607