Year Percent 2001-01-01 0.27 2002-01-01 0.28 2003-01-01 0.29 2004-01-01 0.28 2005-01-01 0.29 2006-01-01 0.34 2007-01-01 0.35 2008-01-01 1.74 2009-01-01 1.94 2010-01-01 1.96 2011-01-01 1.91 2012-01-01 1.99 2013-01-01 2.13 2014-01-01 2.20 2015-01-01 2.26 2016-01-01 2.45