Year	US Dollars
1990	17840
1991	17060
1992	16550
1993	16640
1994	17720
1995	18980
1996	19600
1997	21440
1998	23090
1999	24520
2000	26580
2001	27780
2002	28650
2003	28810
2004	31350
2005	32130
2006	34690
2007	37820
2008	40040
2009	38310
2010	39300
2011	40870
2012	40830
2013	41430
2014	41850
2015	42450
2016	43720
2017	45400