Year Percent 1960-01-01 15.567600000000000 1961-01-01 14.155500000000000 1962-01-01 16.455400000000000 1963-01-01 20.361900000000000 1964-01-01 15.794700000000000 1965-01-01 16.098500000000000 1966-01-01 15.209400000000000 1967-01-01 13.898000000000000 1968-01-01 13.889700000000000 1969-01-01 14.083500000000000 1970-01-01 4.803820000000000 1971-01-01 4.899430000000001 1972-01-01 5.153969999999999 1973-01-01 5.986190000000001 1974-01-01 7.585610000000001 1975-01-01 9.165389999999999 1976-01-01 12.502100000000000 1977-01-01 18.462500000000000 1978-01-01 21.815700000000000 1979-01-01 17.202800000000000 1980-01-01 14.577200000000000 1981-01-01 14.555900000000000 1982-01-01 15.046300000000000 1983-01-01 15.595000000000000 1984-01-01 16.429700000000000 1985-01-01 17.521600000000000 1986-01-01 17.471300000000000 1987-01-01 23.025000000000000 1988-01-01 18.864800000000000 1989-01-01 17.667300000000000 1990-01-01 16.446900000000000 1991-01-01 17.455500000000000 1992-01-01 16.597200000000000 1993-01-01 14.896800000000000 1994-01-01 12.709300000000000 1995-01-01 13.065999999999999 1996-01-01 12.466200000000000 1997-01-01 13.642000000000001 1998-01-01 16.764500000000000 1999-01-01 14.808800000000000 2000-01-01 12.668100000000000 2001-01-01 14.995200000000000 2002-01-01 15.782700000000000 2003-01-01 15.849800000000000 2004-01-01 15.184100000000000 2005-01-01 15.231500000000000 2006-01-01 16.895400000000000 2007-01-01 17.131400000000000 2008-01-01 15.815700000000000 2009-01-01 19.951000000000000 2010-01-01 17.946100000000000 2011-01-01 18.458300000000000 2012-01-01 21.387500000000000 2013-01-01 23.215800000000000 2014-01-01 23.809600000000000 2015-01-01 24.720000000000000 2016-01-01 25.017400000000000