Year	constant 2015 US$
1973	220000
1974	8320000
1975	9600000
1976	8580000
1977	10540000
1978	7290000
1979	6910000
1980	8510000
1981	14430000
1982	14160000
1983	17860000
1984	58880000
1985	71560000
1986	46730000
1987	33620000
1988	32250000
1989	23100000
1990	19100000
1991	21240000
1992	16440000
1993	10250000
1994	30100000
1995	11190000
1996	13030000
1997	10600000
1998	7710000
1999	12930000
2000	20440000
2001	14840000
2002	13410000
2003	11510000
2004	16490000
2005	55150000
2006	27770000
2007	24760000
2008	28300000
2009	41980000
2010	30440000
2011	9270000
2012	6790000
2013	11220000
2014	35370000
2015	24160000
2016	8580000
2017	5710000