Year Percent 1973-01-01 26.306200000000000 1974-01-01 29.591700000000000 1975-01-01 25.085100000000000 1976-01-01 21.113700000000000 1977-01-01 22.956999999999997 1978-01-01 23.892800000000000 1979-01-01 20.538400000000000 1980-01-01 20.286300000000000 1981-01-01 22.846400000000000 1982-01-01 24.818900000000000 1983-01-01 26.522800000000000 1984-01-01 26.963500000000000 1985-01-01 26.382500000000000 1986-01-01 29.616900000000000 1987-01-01 32.565300000000000 1988-01-01 35.894100000000000 1989-01-01 39.326600000000000 1990-01-01 39.441900000000000 1991-01-01 41.748500000000000 1992-01-01 42.561700000000000 1993-01-01 43.481300000000000 1994-01-01 48.334800000000000 1995-01-01 49.687500000000000 1996-01-01 51.126500000000000 1997-01-01 51.020100000000000 1998-01-01 64.875100000000000 1999-01-01 84.869500000000000 2000-01-01 90.689900000000000 2001-01-01 100.437000000000010 2002-01-01 102.243000000000000 2003-01-01 109.180000000000000 2004-01-01 90.384800000000000 2005-01-01 79.394300000000000 2006-01-01 72.304500000000000 2007-01-01 58.849700000000000 2008-01-01 51.001000000000005 2009-01-01 42.492000000000000 2010-01-01 40.552600000000000 2011-01-01 40.357700000000000 2012-01-01 37.431900000000000 2013-01-01 38.500100000000000 2014-01-01 41.265500000000000 2015-01-01 44.474400000000000 2016-01-01 46.472500000000000