Year Percent 1995 15.63624 2000 16.73695 2005 17.91107 2006 17.69628 2007 17.27262 2008 17.62774 2009 19.93359 2010 22.39941 2011 20.05691 2012 18.23062 2013 18.75472 2014 18.3283