Year	constant 2015 US$
1960	15030000
1961	13070000
1963	6300000
1966	1970000
1967	790000
1968	920000
1969	430000
1970	1230000
1971	1320000
1972	450000
1973	520000
1974	120000
1975	70000
1979	50000
1980	9740000
1981	20000
1982	1660000
1983	1280000
1984	1050000
1985	970000
1986	670000
1987	190000
1988	490000
1989	460000
1990	300000
1991	140000
1992	150000
1993	190000
1994	370000
1995	-4580000
1996	340000
1997	420000
1998	620000
1999	350000