Year US Dollars adjusted for inflation) 1970 15656.4729 1971 17401.31882 1972 18055.46181 1973 19008.82791 1974 19890.55506 1975 19978.73473 1976 21126.71501 1977 23130.19933 1978 24621.56044 1979 25610.10316 1980 27499.38348 1981 27248.09862 1982 25790.9724 1983 26375.33672 1984 24724.46102 1985 25387.61404 1986 27036.99071 1987 28211.92116 1988 29412.24234 1989 31087.32042 1990 27295.95234 1991 27314.10719 1992 26011.62756 1993 24748.53368 1994 26073.0271 1995 26899.80186 1996 27262.4139 1997 27613.4807 1998 29702.68897 1999 30111.9577 2000 32193.00252 2001 32514.75985 2002 32051.66566 2003 33380.20993 2004 35645.60107 2005 37352.89254 2006 39539.91571 2007 40626.78143 2008 43305.70276 2009 43684.5872 2010 43988.33249 2011 43781.46256 2012 44454.37355 2013 43954.02161 2014 46443.76342 2015 46738.06226 2016 50255.117