Year Percent 2000 18.19808 2001 18.19808 2002 19.74519 2003 21.2923 2004 22.8394 2005 24.38651 2006 25.93362 2007 27.48186 2008 29.03023 2009 30.57873 2010 32.12735 2011 33.67611 2012 35.22499 2013 36.77399 2014 38.32313 2015 39.87239 2016 41.42178 2017 42.9713 2018 44.52095 2019 46.07072 2020 47.61866 2021 49.1666 2022 50.71454