Year Percent 2000-01-01 0.33 2001-01-01 0.25 2002-01-01 0.22 2003-01-01 0.25 2004-01-01 0.17 2005-01-01 0.13 2006-01-01 0.12 2007-01-01 0.10 2008-01-01 0.10 2009-01-01 0.12 2010-01-01 0.11 2011-01-01 0.14 2012-01-01 0.16 2013-01-01 0.21 2014-01-01 0.20 2015-01-01 0.22