Year Percent 1973-01-01 6.614269999999999 1974-01-01 7.259610000000000 1975-01-01 10.166700000000000 1976-01-01 12.934600000000000 1977-01-01 15.417800000000000 1978-01-01 18.235800000000000 1979-01-01 17.229800000000000 1980-01-01 15.479100000000000 1981-01-01 16.668900000000000 1982-01-01 20.053400000000000 1983-01-01 23.151900000000000 1984-01-01 23.953700000000000 1985-01-01 24.463500000000000 1986-01-01 32.180900000000000 1987-01-01 31.550800000000000 1988-01-01 33.625500000000000 1989-01-01 31.673900000000000 1990-01-01 25.798500000000000 1991-01-01 26.659200000000000 1992-01-01 27.218600000000000 1993-01-01 28.394600000000000 1994-01-01 28.811400000000000 1995-01-01 29.021500000000000 1996-01-01 28.910600000000000 1997-01-01 30.180600000000000 1998-01-01 35.679600000000000 1999-01-01 34.945300000000000 2000-01-01 30.153900000000000 2001-01-01 32.995400000000000 2002-01-01 34.235200000000000 2003-01-01 34.022400000000000 2004-01-01 34.065200000000000 2005-01-01 37.309900000000000 2006-01-01 47.286900000000000 2007-01-01 48.378000000000000 2008-01-01 58.518600000000000 2009-01-01 83.540600000000000 2010-01-01 73.890800000000000 2011-01-01 62.264800000000000 2012-01-01 59.927000000000000 2013-01-01 58.997200000000000 2014-01-01 61.403800000000000 2015-01-01 76.551000000000000 2016-01-01 83.494000000000000