Year Percent 1980-01-01 0.40860799999999997 1981-01-01 0.38609899999999997 1982-01-01 0.49896499999999994 1983-01-01 0.54664499999999990 1984-01-01 0.44246800000000003 1985-01-01 0.33971599999999996 1986-01-01 0.40135600000000000 1987-01-01 0.25305900000000003 1988-01-01 0.12489400000000000 1989-01-01 0.09883700000000000 1990-01-01 11.28560000000000000 1991-01-01 9.83804000000000000 1992-01-01 8.67871000000000000 1993-01-01 7.22913999999999900 1994-01-01 6.94873999999999900 1995-01-01 9.87011000000000000 1996-01-01 11.65520000000000000 1997-01-01 9.72956999999999900 1998-01-01 9.27575000000000000 1999-01-01 9.11506000000000000 2000-01-01 7.78871000000000100 2001-01-01 6.73846000000000100 2002-01-01 6.56546999999999950 2003-01-01 5.61208000000000100 2004-01-01 5.65020999999999950 2005-01-01 4.94215000000000000 2006-01-01 4.28947000000000000 2007-01-01 3.94847000000000000 2008-01-01 3.56970000000000000 2009-01-01 4.70990000000000000 2010-01-01 4.20182000000000000 2011-01-01 3.87795000000000000 2012-01-01 4.10514000000000050 2013-01-01 4.20555000000000000 2014-01-01 4.33554000000000000 2015-01-01 5.33741000000000000 2016-01-01 6.27980999999999940