Year	U.S. dollars (Units)
1980	479.064
1981	550.438
1982	584.379
1983	530.372
1984	560.154
1985	545.174
1986	543.594
1987	553.482
1988	621.142
1989	631.367
1990	615.815
1991	684.450
1992	713.395
1993	735.815
1994	723.052
1995	823.987
1996	839.336
1997	807.501
1998	784.545
1999	725.396
2000	733.461
2001	696.936
2002	689.971
2003	771.761
2004	885.149
2005	948.828
2006	1032.277
2007	1146.082
2008	1228.232
2009	1108.978
2010	1137.985
2011	1301.736
2012	1377.776
2013	1390.648
2014	1423.889
2015	1535.348
2016	1566.625
2017	1653.406
2018	1698.034
2019	1500.683
2020	1376.512
2021	1565.575
2022	1650.678
2023	1460.740