Year Percent 1960-01-01 17.761400000000000 1961-01-01 17.852700000000000 1962-01-01 16.439300000000000 1963-01-01 15.949100000000000 1964-01-01 15.255999999999998 1965-01-01 15.291600000000000 1966-01-01 15.912400000000000 1967-01-01 15.443000000000000 1968-01-01 15.272900000000000 1969-01-01 14.665700000000000 1970-01-01 12.813900000000000 1971-01-01 13.291700000000000 1972-01-01 14.604100000000000 1973-01-01 15.634500000000000 1974-01-01 15.203300000000000 1975-01-01 17.273600000000000 1976-01-01 17.901600000000000 1977-01-01 18.197000000000000 1978-01-01 19.742700000000000 1979-01-01 20.086500000000000 1980-01-01 19.084300000000000 1981-01-01 21.041300000000000 1982-01-01 20.885400000000000 1983-01-01 22.523600000000000 1984-01-01 23.890500000000000 1985-01-01 23.296700000000000 1986-01-01 23.135700000000000 1987-01-01 25.865400000000000 1988-01-01 25.162800000000000 1989-01-01 26.428400000000000 1990-01-01 28.425800000000000 1991-01-01 30.672100000000000 1992-01-01 34.390000000000000 1993-01-01 37.265900000000000 1994-01-01 36.647900000000000 1995-01-01 39.897900000000000 1996-01-01 37.323500000000000 1997-01-01 43.028800000000000 1998-01-01 46.542600000000000 1999-01-01 49.058400000000000 2000-01-01 53.745100000000000 2001-01-01 55.347900000000000 2002-01-01 59.084600000000000 2003-01-01 59.424000000000000 2004-01-01 61.167000000000000 2005-01-01 64.877600000000000 2006-01-01 68.838100000000000 2007-01-01 74.646200000000000 2008-01-01 77.634000000000000 2009-01-01 79.850200000000000 2010-01-01 82.808400000000000 2011-01-01 85.629300000000000 2012-01-01 86.433100000000000 2013-01-01 85.096800000000000 2014-01-01 86.530300000000000 2015-01-01 86.559900000000000 2016-01-01 88.626500000000000