Year	U.S. dollars (Units)
1981	1112.642
1982	1217.573
1983	1346.688
1984	1495.272
1985	1642.752
1986	1864.889
1987	2102.964
1988	2377.904
1989	2582.185
1990	2819.552
1991	3087.299
1992	3287.848
1993	3448.673
1994	3713.105
1995	3855.291
1996	4104.420
1997	4254.367
1998	4526.684
1999	4657.561
2000	4681.178
2001	4775.344
2002	4680.264
2003	4825.770
2004	5165.218
2005	5127.438
2006	5497.251
2007	5939.910
2008	6463.440
2009	6903.996
2010	6980.957
2011	7160.275
2012	6994.866
2013	7153.468
2014	7388.583
2015	7596.222
2016	8089.250
2017	7507.368
2018	7981.044
2019	8466.407
2020	6872.220
2021	7530.367
2022	8196.917
2023	8837.332
2024	9455.158
2025	10012.808
2026	10495.588
2027	10963.586
2028	11451.690
2029	11901.567