Year US Dollars adjusted for inflation) 1960 219000000 1961 37000000 1962 4000000 1963 52000000 1964 263000000 1965 228000000 1966 373000000 1967 177000000 1968 199000000 1969 166000000 1970 141000000 1971 147000000 1972 185000000 1973 115000000 1974 63000000 1975 136000000 1976 142000000 1977 4000000 1978 217000000 1979 226000000 1980 272000000 1981 289000000 1982 175000000 1983 442000000 1984 404000000 1985 341000000 1986 108000000 1987 151000000 1988 179000000 1989 318000000 1990 438000000 1991 474000000 1992 386000000 1993 102000000 1994 118000000 1995 93000000 1996 187000000 1997 379000000 1998 435000000 1999 506000000 2000 22000000 2001 67000000 2002 62000000 2003 117000000 2004 203000000 2005 168000000 2006 83000000 2007 108000000 2008 17000000 2009 39000000 2010 48000000 2011 32000000 2012 10000000 2013 6000000 2014 5000000 2015 12000000 2016 73000000 2017 34000000 2018 10000000 2019 10000000 2020 10000000 2021 10000000