Year Percent 1980-01-01 12.147500000000000 1981-01-01 13.557600000000000 1982-01-01 16.178600000000000 1983-01-01 16.124600000000000 1984-01-01 16.504800000000000 1985-01-01 17.639400000000000 1986-01-01 21.077200000000000 1987-01-01 20.166900000000000 1988-01-01 18.310200000000000 1989-01-01 16.867800000000000 1990-01-01 17.297400000000000 1991-01-01 19.370300000000000 1992-01-01 20.615500000000000 1993-01-01 24.388200000000000 1994-01-01 27.294100000000000 1995-01-01 27.813000000000002 1996-01-01 27.154500000000000 1997-01-01 26.876200000000000 1998-01-01 31.456000000000000 1999-01-01 30.410700000000000 2000-01-01 25.991300000000000 2001-01-01 28.760700000000000 2002-01-01 29.867300000000000 2003-01-01 29.223700000000000 2004-01-01 27.950700000000000 2005-01-01 25.663900000000000 2006-01-01 25.915800000000000 2007-01-01 28.999300000000000 2008-01-01 28.806400000000000 2009-01-01 38.887100000000000 2010-01-01 37.688200000000000 2011-01-01 36.134000000000000 2012-01-01 37.931400000000000 2013-01-01 40.515700000000000 2014-01-01 42.013900000000000 2015-01-01 49.150300000000000 2016-01-01 53.925700000000000