Year Percent 1977-01-01 1.277500000000000 1978-01-01 2.772800000000000 1979-01-01 4.472370000000000 1980-01-01 6.799440000000000 1981-01-01 9.056650000000000 1982-01-01 9.902160000000000 1983-01-01 10.560700000000000 1984-01-01 11.520400000000000 1985-01-01 11.937700000000000 1986-01-01 12.881600000000000 1987-01-01 11.779000000000002 1988-01-01 13.652800000000000 1989-01-01 15.486700000000000 1990-01-01 7.662100000000000 1991-01-01 3.340620000000000 1992-01-01 4.900690000000000 1993-01-01 6.490620000000000 1994-01-01 5.596030000000001 1995-01-01 4.876490000000000 1996-01-01 5.665170000000000 1997-01-01 6.517280000000000 1998-01-01 6.638570000000000 1999-01-01 6.557989999999999 2000-01-01 7.382389999999999 2001-01-01 13.591700000000000 2002-01-01 18.409800000000000 2003-01-01 16.791200000000000 2004-01-01 15.425600000000000 2005-01-01 14.245400000000000 2006-01-01 13.349800000000000 2007-01-01 11.395700000000000 2008-01-01 9.981000000000000 2009-01-01 10.258700000000000 2010-01-01 10.372900000000000 2011-01-01 8.758480000000000 2012-01-01 7.929730000000000 2013-01-01 12.920500000000000 2014-01-01 18.380800000000000 2015-01-01 17.205300000000000 2016-01-01 16.402000000000000