Year Percent 2000 18.92308 2001 20.09249 2002 21.29293 2003 22.52441 2004 23.78692 2005 25.08046 2006 26.40504 2007 27.76065 2008 29.14729 2009 30.56497 2010 32.01368 2011 33.49343 2012 35.00421 2013 36.54602 2014 38.11886 2015 39.72274 2016 41.35766 2017 43.0236 2018 44.72059 2019 46.4486 2020 48.20765 2021 49.99773 2022 51.81884