Year Percent 1960-01-01 10.526100000000000 1961-01-01 11.511300000000000 1962-01-01 11.342000000000000 1963-01-01 10.982200000000000 1964-01-01 10.406500000000000 1965-01-01 9.458900000000000 1966-01-01 8.960139999999999 1967-01-01 9.084980000000000 1968-01-01 10.649300000000000 1969-01-01 10.974200000000000 1970-01-01 11.598900000000000 1971-01-01 11.648600000000000 1972-01-01 13.029500000000000 1973-01-01 14.182500000000000 1974-01-01 13.855100000000000 1975-01-01 14.051100000000000 1976-01-01 15.753000000000000 1977-01-01 20.104900000000000 1978-01-01 22.470500000000000 1979-01-01 23.388200000000000 1980-01-01 23.685200000000000 1981-01-01 24.608800000000000 1982-01-01 25.189400000000000 1983-01-01 24.899000000000000 1984-01-01 24.064800000000000 1985-01-01 24.353200000000000 1986-01-01 24.713000000000000 1987-01-01 53.344100000000000 1988-01-01 83.330800000000000 1989-01-01 97.702200000000000 1990-01-01 93.462700000000000 1991-01-01 88.997800000000000 1992-01-01 115.052000000000000 1993-01-01 99.609400000000000 1994-01-01 41.402600000000000 1995-01-01 32.505600000000000 1996-01-01 30.770900000000000 1997-01-01 30.553600000000000 1998-01-01 29.785000000000000 1999-01-01 31.583000000000002 2000-01-01 34.170400000000000 2001-01-01 36.702600000000000 2002-01-01 39.312900000000000 2003-01-01 44.248800000000000 2004-01-01 43.287600000000000 2005-01-01 39.551700000000000 2006-01-01 37.637500000000000 2007-01-01 35.914500000000000 2008-01-01 36.634500000000000 2009-01-01 36.205000000000000 2010-01-01 44.252700000000000 2011-01-01 45.608600000000000 2012-01-01 44.368400000000000 2013-01-01 43.028200000000000 2014-01-01 42.958600000000000 2015-01-01 45.735300000000000 2016-01-01 48.712600000000000