Year	US Dollars
1962	500
1963	570
1964	640
1965	730
1966	840
1967	930
1968	1010
1969	1110
1970	1170
1971	1310
1972	1590
1973	2090
1974	2740
1975	3250
1976	3440
1977	3650
1978	4040
1979	5010
1980	6220
1981	6320
1982	5690
1983	4860
1984	4590
1985	4560
1986	5410
1987	7110
1988	9420
1989	10710
1990	12220
1991	13710
1992	15620
1993	15030
1994	14490
1995	14840
1996	15580
1997	15830
1998	15460
1999	15480
2000	15790
2001	15540
2002	15580
2003	18060
2004	22120
2005	25930
2006	27970
2007	29920
2008	32450
2009	32770
2010	32130
2011	31150
2012	29760
2013	29400
2014	29300
2015	28420
2016	27580
2017	27180