Year Percent 1997-01-01 0.1955090000000000 1998-01-01 0.2485720000000000 1999-01-01 0.2891050000000000 2000-01-01 0.3148710000000000 2001-01-01 0.4194250000000000 2002-01-01 0.6370470000000000 2003-01-01 0.5309800000000000 2004-01-01 0.5386660000000000 2005-01-01 0.7120560000000000 2006-01-01 1.0463700000000000 2007-01-01 1.0375400000000000 2008-01-01 0.8012800000000000 2009-01-01 0.6728410000000000 2010-01-01 0.5608800000000000 2011-01-01 0.5432520000000001 2012-01-01 0.5107619999999999 2013-01-01 0.5397010000000000 2014-01-01 0.4677470000000000 2015-01-01 0.5339950000000000