Year Percent 2001-01-01 0.02566600000000000 2002-01-01 0.03821100000000000 2003-01-01 0.04030400000000000 2004-01-01 0.04030400000000000 2005-01-01 0.11458099999999999 2006-01-01 0.13114700000000000 2007-01-01 0.16959200000000002 2008-01-01 0.16751000000000000 2009-01-01 0.16446200000000000 2010-01-01 0.19782100000000000 2011-01-01 0.20395200000000000 2012-01-01 0.21242399999999997 2013-01-01 0.23130000000000000 2014-01-01 0.23487300000000000 2015-01-01 0.23368300000000000