Year	U.S. dollars (Units)
1980	1373.087
1981	1546.061
1982	1439.284
1983	1528.786
1984	1922.756
1985	2141.232
1986	2520.480
1987	2743.223
1988	3096.607
1989	3463.514
1990	4069.783
1991	4249.598
1992	4599.798
1993	4604.862
1994	4736.704
1995	5003.443
1996	5119.759
1997	5181.542
1998	5588.756
1999	5821.497
2000	5843.353
2001	5553.186
2002	5558.316
2003	6051.870
2004	6490.831
2005	6861.984
2006	7614.247
2007	7944.157
2008	8462.296
2009	8248.564
2010	8555.920
2011	9113.380
2012	9232.222
2013	9542.229
2014	10008.505
2015	10291.460
2016	10591.881
2017	11282.751
2018	11585.525
2019	11773.428
2020	8496.098
2021	10295.001
2022	12703.961
2023	13545.906
2024	14101.380
2025	14660.583
2026	15197.064
2027	15711.662
2028	16243.685
2029	16793.723