Year Percent 2000 19.67945 2001 19.28179 2002 17.71481 2003 23.61192 2004 27.22694 2005 26.74847 2006 28.47821 2007 26.47336 2008 27.73071 2009 36.95457 2010 50.2 2011 47.39952 2012 44.8013 2013 47.01407 2014 48.52314 2015 53.09243 2016 52.8 2017 53.61446