Year	US Dollars
1990	7300
1991	7490
1992	7480
1993	7630
1994	8080
1995	8560
1996	9300
1997	10400
1998	11480
1999	12540
2000	13400
2001	14480
2002	15930
2003	18370
2004	20930
2005	22420
2006	25940
2007	27940
2008	29340
2009	27870
2010	29140
2011	27260
2012	29050
2013	30580
2014	30760
2015	33240
2016	31420
2017	30520