Year Percent 2000 3.30026 2001 3.36165 2002 3.42304 2003 3.48442 2004 3.54581 2005 3.6072 2006 3.88025 2007 4.1604 2008 4.44762 2009 4.74193 2010 5.04332 2011 5.3518 2012 5.66736 2013 5.99001 2014 6.31974 2015 6.65655 2016 7.00045 2017 7.35143 2018 7.70949 2019 8.07464 2020 8.44687 2021 8.82619 2022 9.21259