Year Percent 1999-01-01 0.51682100000000000 2000-01-01 0.50442500000000000 2001-01-01 0.45516100000000000 2002-01-01 0.47354799999999997 2003-01-01 0.49266600000000000 2004-01-01 0.48361600000000000 2005-01-01 0.45453599999999994 2006-01-01 0.43395200000000006 2007-01-01 0.44644500000000000 2008-01-01 0.40049500000000000 2009-01-01 0.43206100000000000 2010-01-01 0.44565900000000000 2011-01-01 0.39471300000000004 2012-01-01 0.38476600000000000 2013-01-01 0.39455800000000000 2014-01-01 0.37910600000000000 2015-01-01 0.41341200000000000