Year Percent 1997-01-01 0.05309199999999999 1998-01-01 0.08825900000000000 1999-01-01 0.11216600000000000 2000-01-01 0.12398300000000000 2001-01-01 0.11282100000000000 2002-01-01 0.15528200000000000 2003-01-01 0.15425200000000000 2004-01-01 0.20494300000000000 2005-01-01 0.19406300000000000 2006-01-01 0.22210200000000000 2007-01-01 0.12567500000000000 2008-01-01 0.11876099999999999 2009-01-01 0.22305900000000000 2010-01-01 0.19157100000000000 2011-01-01 0.53516900000000000 2012-01-01 0.54742899999999990 2013-01-01 0.51060400000000000 2014-01-01 0.51160800000000000 2015-01-01 0.50067200000000000