Year	US Dollars
1967	3650
1968	3660
1969	3540
1970	3330
1971	3540
1972	3660
1973	4380
1974	6640
1975	10090
1976	14900
1977	14050
1978	15430
1979	19240
1980	19460
1981	21280
1982	18810
1983	17730
1984	16670
1985	14670
1986	16790
1987	15420
1988	14300
1989	17350
1995	20460
1996	20810
1997	21420
1998	19620
1999	16820
2000	17930
2001	18670
2002	18890
2003	22520
2004	28100
2005	34400
2006	41350
2007	47590
2008	51790
2009	46000
2010	42060
2011	43510
2012	49950
2013	51990
2014	49770
2015	40750
2016	34890
2017	31430