Year US Dollars adjusted for inflation) 1991 11204.484 1992 11645.758 1993 11990.529 1994 11747.212 1995 12367.497 1996 12434.672 1997 12653.777 1998 12988.964 1999 13227.56 2000 13312.595 2001 13342.107 2002 13798.662 2003 14531.101 2004 14865.912 2005 14982.791 2006 15800.575 2007 15365.783 2008 16226.024 2009 15741.141 2010 15074.605 2011 14866.602 2012 14917.465 2013 15041.324 2014 15153.238 2015 15289.682 2016 15610.51 2017 15963.615 2018 16385.977 2019 16844.025 2020 17343.348 2021 17889.002 2022 18458.092