Year	US Dollars
1962	490
1963	530
1964	500
1965	540
1966	590
1967	660
1968	750
1969	850
1970	960
1971	1090
1972	1280
1973	1610
1974	2090
1975	2670
1976	2940
1977	3030
1978	3390
1979	4000
1980	4720
1981	5370
1982	5680
1983	6160
1984	6920
1985	7090
1986	7320
1987	8070
1988	9300
1989	10300
1990	11450
1991	12980
1992	15320
1993	17760
1994	20780
1995	23610
1996	25640
1997	27750
1998	24010
1999	23410
2000	23670
2001	21990
2002	21760
2003	23110
2004	25650
2005	28370
2006	32080
2007	35660
2008	36680
2009	37080
2010	44790
2011	48310
2012	51110
2013	54730
2014	56370
2015	54020
2016	52350
2017	54530