Year	US Dollars
1990	7660
1991	7590
1992	7440
1993	7680
1994	8160
1995	8530
1996	8950
1997	9360
1998	9740
1999	10170
2000	11010
2001	10940
2002	11070
2003	11780
2004	12700
2005	13640
2006	14560
2007	15560
2008	15980
2009	15570
2010	15740
2011	15340
2012	15980
2013	15920
2014	15660
2015	15310
2016	15210
2017	15540