Year Percent 1998-01-01 0.24520000000000000 1999-01-01 0.24987199999999998 2000-01-01 0.26879000000000003 2001-01-01 0.27391100000000000 2002-01-01 0.29460800000000000 2003-01-01 0.27250800000000000 2004-01-01 0.18043299999999998 2005-01-01 0.13888800000000000 2006-01-01 0.12462100000000001 2007-01-01 0.16340000000000000 2008-01-01 0.12385100000000000 2009-01-01 0.21082500000000000 2010-01-01 0.12573099999999998 2011-01-01 0.10323800000000001 2012-01-01 0.12435299999999999 2013-01-01 0.13922900000000000 2014-01-01 0.14545100000000000 2015-01-01 0.16686900000000002