Year Percent 1976-01-01 8.779250000000000 1977-01-01 10.996300000000000 1978-01-01 10.603500000000000 1979-01-01 8.995040000000000 1980-01-01 11.918400000000000 1981-01-01 11.178300000000000 1982-01-01 9.268369999999999 1983-01-01 9.702169999999999 1984-01-01 10.424300000000000 1985-01-01 10.341200000000000 1986-01-01 10.879600000000000 1987-01-01 12.011800000000000 1988-01-01 12.678600000000000 1989-01-01 12.930100000000000 1990-01-01 12.458400000000000 1991-01-01 12.549600000000000 1992-01-01 12.268300000000000 1993-01-01 13.603900000000000 1994-01-01 15.879200000000000 1995-01-01 15.946400000000000 1996-01-01 18.551400000000000 1997-01-01 19.749800000000000 1998-01-01 23.549800000000000 1999-01-01 24.729000000000000 2000-01-01 24.278900000000000 2001-01-01 25.490400000000000 2002-01-01 28.291200000000000 2003-01-01 26.527300000000000 2004-01-01 32.210500000000000 2005-01-01 36.484100000000000 2006-01-01 31.295100000000000 2007-01-01 32.743600000000000 2008-01-01 34.430500000000000 2009-01-01 38.457700000000000 2010-01-01 40.202300000000000 2011-01-01 38.671200000000000 2012-01-01 39.562700000000000 2013-01-01 38.190300000000000 2014-01-01 39.919800000000000 2015-01-01 42.347000000000000 2016-01-01 42.154100000000000