Year Percent 1991-01-01 0.27446300000000000 1992-01-01 0.27747400000000000 1993-01-01 0.26806599999999997 1994-01-01 0.17407200000000000 1995-01-01 0.19591100000000000 1996-01-01 0.18582900000000000 1997-01-01 0.17344000000000000 1998-01-01 0.18362100000000000 1999-01-01 0.20284700000000000 2000-01-01 0.19792600000000000 2001-01-01 0.17122100000000000 2002-01-01 0.16802500000000000 2003-01-01 0.12826400000000002 2004-01-01 0.12930200000000000 2005-01-01 0.18560600000000000 2006-01-01 0.14743100000000000 2007-01-01 0.13663499999999998 2008-01-01 0.15179800000000000 2009-01-01 0.17229400000000000 2010-01-01 0.18053400000000000 2011-01-01 0.18753399999999998 2012-01-01 0.19589700000000002 2013-01-01 0.19618300000000000 2014-01-01 0.19827100000000000 2015-01-01 0.21750200000000000