Year Percent 1986-01-01 12.11500000000000 1987-01-01 10.92750000000000 1988-01-01 9.75250000000000 1989-01-01 7.90250000000000 1990-01-01 7.75750000000000 1991-01-01 8.15500000000000 1992-01-01 6.66500000000000 1993-01-01 6.54250000000000 1994-01-01 7.81500000000000 1995-01-01 7.30250000000000 1996-01-01 6.32500000000000 1997-01-01 6.11500000000000 1998-01-01 6.39500000000000 1999-01-01 10.13750000000000 2000-01-01 9.66750000000000 2001-01-01 9.85250000000000 2002-01-01 9.80500000000000 2003-01-01 9.54000000000000 2004-01-01 10.00750000000000 2005-01-01 9.23500000000000 2006-01-01 7.80000000000000 2007-01-01 7.13000000000000 2008-01-01 7.79250000000000 2009-01-01 9.67500000000000 2010-01-01 8.15000000000000 2011-01-01 7.12500000000000 2012-01-01 6.43267569808634 2013-01-01 5.93237761509328 2014-01-01 6.39140353169338 2015-01-01 6.21371866366004 2016-01-01 6.49001247584928 2017-01-01 6.67368848036680