Year Percent 2000 31.75456 2001 31.74152 2002 31.73085 2003 31.72019 2004 31.70893 2005 32.73958 2006 33.77066 2007 34.80218 2008 35.83414 2009 36.85912 2010 37.88026 2011 38.89704 2012 39.9105 2013 40.92717 2014 41.9467 2015 42.96877 2016 43.99303 2017 45.01918 2018 46.04734 2019 47.07673 2020 48.10702 2021 49.16923 2022 50.23518