Year current US$ 1970 166.15214696759173 1971 196.02440377058608 1972 213.27879247022435 1973 117.66066383532872 1974 683.0064698034163 1975 999.0359513180689 1976 1373.910119455539 1977 1599.8306404847226 1978 1667.0577029091864 1979 1403.8828788317446 1980 3102.019079965434 1981 4037.6829704683323 1982 4499.673174027019 1983 4189.6865480031975 1984 4528.53156826996 1985 4630.85803607698 1986 3415.541695204677 1987 3040.225860527087 1988 3068.0557914241613 1989 2981.7074554990204 1990 3316.7463220269724 1991 3782.041496885004 1992 3912.4528455062064 1993 3757.9000633725705 1994 3868.5579959210095 1995 4003.4450534087337 1996 4098.296284924714 1997 4368.9923744525 1998 4072.0239558970575 1999 4092.731679423497 2000 4380.929602356145 2001 4712.64740337064 2002 5193.127110510392 2003 5522.110521102155 2004 5966.890848894325 2005 6764.59478765792 2006 8326.426920818043 2007 9378.816424762788 2008 13377.590232223574 2009 9843.836652870266 2010 12379.789313281348 2011 11923.262408338973 2012 12859.287101328186 2013 12617.401593399552 2014 12603.712110808285 2015 12240.889548319352 2016 11524.25384571703 2017 11682.784693016376 2018 13303.373735208253 2019 12834.528683551636 2020 11983.324314548867 2021 12502.122867684806