Year US Dollars adjusted for inflation) 1991 13376.799 1992 13579.563 1993 13667.764 1994 14327.804 1995 14862.613 1996 15331.046 1997 16031.932 1998 15628.246 1999 16374.004 2000 16014.28 2001 16000.126 2002 16936.598 2003 17712.885 2004 17243.48 2005 17097.754 2006 17231.449 2007 18179.896 2008 18821.086 2009 16852.9 2010 19131.867 2011 18471.756 2012 17841.316 2013 18638.393 2014 18882.316 2015 18059.297 2016 18194.229 2017 18222.85 2018 18661.768 2019 19192.094 2020 19711.836 2021 20236.242 2022 20775.393