Year	US Dollars
1990	9120
1991	9050
1992	8660
1993	8890
1994	9410
1995	9730
1996	10250
1997	10910
1998	11390
1999	11520
2000	11980
2001	11880
2002	12110
2003	12580
2004	13040
2005	13740
2006	14670
2007	15570
2008	15740
2009	15230
2010	15730
2011	15410
2012	16150
2013	16270
2014	16500
2015	16710
2016	17170
2017	17830