Year Percent 2005 10.15987 2006 10.53361 2007 10.14543 2008 10.76776 2009 11.68671 2010 12.0632 2011 12.59734 2012 12.79424 2013 11.95224 2014 12.74207 2015 12.92326 2016 12.57954 2017 13.19086