Year Percent 1960-01-01 5.411830000000000 1961-01-01 5.747590000000000 1962-01-01 5.978510000000000 1963-01-01 7.083620000000000 1964-01-01 7.547900000000000 1965-01-01 8.280520000000000 1966-01-01 8.433860000000001 1967-01-01 9.373710000000000 1968-01-01 9.446470000000000 1969-01-01 10.062900000000000 1970-01-01 11.085700000000000 1971-01-01 11.617200000000000 1972-01-01 11.937300000000000 1973-01-01 14.687000000000001 1974-01-01 14.223500000000000 1975-01-01 12.344900000000000 1976-01-01 13.871800000000000 1977-01-01 17.887600000000000 1978-01-01 18.639800000000000 1979-01-01 19.180900000000000 1980-01-01 21.992300000000000 1981-01-01 21.902700000000000 1982-01-01 23.239600000000000 1983-01-01 26.132800000000000 1984-01-01 25.317500000000000 1985-01-01 24.932600000000000 1986-01-01 26.119300000000000 1987-01-01 27.063000000000002 1988-01-01 27.103000000000000 1989-01-01 28.370500000000000 1990-01-01 29.401800000000000 1991-01-01 30.773400000000000 1992-01-01 30.709200000000000 1993-01-01 32.453900000000000 1994-01-01 33.635500000000000 1995-01-01 35.572800000000000 1996-01-01 35.890400000000000 1997-01-01 37.737900000000000 1998-01-01 42.908900000000000 1999-01-01 43.564300000000000 2000-01-01 46.846900000000000 2001-01-01 47.290300000000000 2002-01-01 49.802500000000000 2003-01-01 50.367700000000000 2004-01-01 50.857700000000000 2005-01-01 51.998500000000000 2006-01-01 53.090800000000000 2007-01-01 56.053700000000000 2008-01-01 60.948300000000000 2009-01-01 67.844800000000000 2010-01-01 70.222600000000000 2011-01-01 70.437800000000000 2012-01-01 73.878500000000000 2013-01-01 77.853100000000000 2014-01-01 79.599400000000000 2015-01-01 87.558900000000000 2016-01-01 100.891000000000000