Year	US Dollars
1990	16720
1991	17060
1992	17480
1993	18600
1994	19620
1995	20170
1996	21180
1997	22150
1998	23410
1999	24460
2000	25560
2001	26580
2002	27930
2003	28840
2004	30420
2005	31330
2006	32950
2007	34880
2008	35880
2009	38820
2010	37750
2011	40210
2012	41430
2013	44650
2014	45520
2015	45270
2016	45110
2017	47160