Year	US Dollars
1990	18820
1991	19800
1992	20470
1993	20880
1994	22120
1995	23010
1996	23400
1997	24480
1998	25120
1999	26220
2000	28690
2001	29510
2002	30990
2003	31630
2004	32680
2005	33720
2006	35870
2007	37350
2008	39030
2009	38050
2010	41350
2011	41660
2012	43390
2013	44240
2014	44940
2015	45330
2016	46750
2017	48240