Year Percent 2006 2.9198 2007 5.5471 2008 7.0009 2009 7.3732 2010 3.0956 2011 3.1118 2012 6.0761 2013 5.2571 2014 3.5343 2015 3.2439 2016 2.3337 2017 2.7428