Year Percent 1998 13.74373 1999 13.47692 2000 11.21975 2003 11.25883 2008 12.93561 2009 12.59804 2010 12.12291 2011 14.5554 2012 13.27213 2013 14.09308 2014 14.98144 2015 15.09517 2016 13.32624