Year	US Dollars
1990	4730
1991	5110
1992	5500
1993	5830
1994	6070
1995	6420
1996	6790
1997	7260
1998	7680
1999	7910
2000	8720
2001	9170
2002	9440
2003	9820
2004	10640
2005	11060
2006	12390
2007	13650
2008	14470
2009	14750
2010	15800
2011	16610
2012	17470
2013	18280
2014	18740
2015	19940
2016	20990
2017	22570