Year US Dollars adjusted for inflation) 1991 49340.227 1992 49148.832 1993 48021.688 1994 46474.117 1995 46243.754 1996 47774.379 1997 51266.699 1998 53326.121 1999 53590.445 2000 56365.652 2001 57779.598 2002 55310.891 2003 51569.547 2004 49859.465 2005 48635.086 2006 48044.684 2007 46788.047 2008 46962.41 2009 45781.09 2010 43678.094 2011 38889.305 2012 38250.48 2013 35980.695 2014 33522.898 2015 32596.777 2016 32734.738 2017 31274.555 2018 30898.789 2019 30320.049 2020 29890.471 2021 30523.412 2022 30958.613