Year Percent 1960-01-01 9.995190000000000 1961-01-01 10.015500000000000 1962-01-01 9.946100000000000 1963-01-01 10.256600000000000 1964-01-01 10.681800000000000 1965-01-01 11.910800000000000 1966-01-01 13.862000000000000 1967-01-01 16.265500000000000 1968-01-01 17.886700000000000 1969-01-01 20.011400000000000 1970-01-01 14.363500000000000 1971-01-01 15.282500000000000 1972-01-01 15.170300000000000 1973-01-01 16.046000000000000 1974-01-01 17.420000000000000 1975-01-01 19.200200000000000 1976-01-01 19.541400000000000 1977-01-01 20.314700000000000 1978-01-01 21.017300000000000 1979-01-01 20.853100000000000 1980-01-01 20.663400000000000 1981-01-01 20.164500000000000 1982-01-01 21.455500000000000 1983-01-01 22.504400000000000 1984-01-01 22.814000000000000 1985-01-01 22.999700000000000 1986-01-01 24.386000000000000 1987-01-01 24.842200000000000 1988-01-01 24.393000000000000 1989-01-01 23.468400000000000 1990-01-01 21.471300000000000 1991-01-01 19.071700000000000 1992-01-01 18.605100000000000 1993-01-01 18.551100000000000 1994-01-01 17.604500000000000 1995-01-01 16.884100000000000 1996-01-01 17.627700000000000 1997-01-01 21.648600000000000 1998-01-01 27.214400000000000 1999-01-01 31.779700000000000 2000-01-01 32.216900000000000 2001-01-01 33.815900000000000 2002-01-01 34.658500000000000 2003-01-01 34.546600000000000 2004-01-01 34.955200000000000 2005-01-01 35.974000000000004 2006-01-01 39.186000000000000 2007-01-01 45.181300000000000 2008-01-01 49.384200000000000 2009-01-01 49.745600000000000 2010-01-01 47.078800000000000 2011-01-01 45.096100000000000 2012-01-01 47.446900000000000 2013-01-01 51.871200000000000 2014-01-01 52.627100000000000 2015-01-01 52.299600000000000 2016-01-01 53.729900000000000