Year Percent 1975-01-01 33.999600000000000 1976-01-01 36.210600000000000 1977-01-01 37.800400000000000 1978-01-01 36.675700000000000 1979-01-01 36.198100000000000 1980-01-01 36.671700000000000 1981-01-01 37.089200000000000 1982-01-01 33.844500000000000 1983-01-01 36.728900000000000 1984-01-01 40.509600000000000 1985-01-01 44.338900000000000 1986-01-01 54.741900000000000 1987-01-01 52.894300000000000 1988-01-01 40.410300000000000 1989-01-01 34.595500000000000 1990-01-01 33.313500000000000 1991-01-01 34.566900000000000 1992-01-01 37.756100000000000 1993-01-01 40.061300000000000 1994-01-01 41.493200000000000 1995-01-01 42.503800000000000 1996-01-01 41.814100000000000 1997-01-01 43.619500000000000 1998-01-01 50.221600000000000 1999-01-01 52.785500000000000 2000-01-01 48.916100000000000 2001-01-01 48.916100000000000 2002-01-01 48.916100000000000 2003-01-01 48.916100000000000 2004-01-01 54.086999999999996 2005-01-01 48.991000000000010 2006-01-01 49.621900000000000 2007-01-01 53.612300000000000 2008-01-01 61.101200000000000 2009-01-01 82.428900000000000 2010-01-01 80.518999999999990 2011-01-01 81.769700000000000 2012-01-01 87.106600000000000 2013-01-01 90.790700000000000 2014-01-01 92.607900000000000 2015-01-01 103.032000000000010