Year	US Dollars
1990	17730
1991	18490
1992	19150
1993	19420
1994	20190
1995	20950
1996	21640
1997	22640
1998	23770
1999	24930
2000	26700
2001	28140
2002	28930
2003	28610
2004	29580
2005	31140
2006	33180
2007	34870
2008	35910
2009	35350
2010	36730
2011	38320
2012	38180
2013	40040
2014	40680
2015	41100
2016	42020
2017	43790