Year	US Dollars
1998	3.52
1999	3.9
2000	4.37
2001	4.5
2002	4.71
2003	4.94
2004	5.1
2005	5.28
2006	5.4
2007	5.84
2008	6.94
2009	7.56
2010	8.32
2011	8.52
2012	9.67
2013	10.29
2014	11.34
2015	11.74
2016	12.53