Year Percent 1973-01-01 9.173230000000000 1974-01-01 12.067000000000000 1975-01-01 16.683500000000000 1976-01-01 20.465700000000000 1977-01-01 18.937700000000000 1978-01-01 17.167500000000000 1979-01-01 15.203600000000000 1980-01-01 13.931900000000000 1981-01-01 15.925999999999998 1982-01-01 20.419800000000000 1983-01-01 24.860100000000000 1984-01-01 29.815700000000000 1985-01-01 35.321700000000000 1986-01-01 46.969200000000000 1987-01-01 44.895700000000000 1988-01-01 46.680400000000000 1989-01-01 43.390200000000000 1990-01-01 33.626300000000000 1991-01-01 34.023400000000000 1992-01-01 35.468900000000000 1993-01-01 35.154500000000000 1994-01-01 33.720300000000000 1995-01-01 33.213100000000000 1996-01-01 32.290600000000000 1997-01-01 32.485500000000000 1998-01-01 35.911100000000000 1999-01-01 34.319500000000000 2000-01-01 31.066500000000000 2001-01-01 37.349100000000000 2002-01-01 40.923800000000000 2003-01-01 40.976300000000000 2004-01-01 41.353700000000000 2005-01-01 43.152000000000000 2006-01-01 48.949700000000000 2007-01-01 50.939700000000000 2008-01-01 55.871200000000000 2009-01-01 75.600200000000000 2010-01-01 71.463000000000010 2011-01-01 62.303200000000000 2012-01-01 61.248300000000000 2013-01-01 66.856100000000000 2014-01-01 74.212300000000000 2015-01-01 89.886000000000010 2016-01-01 94.860400000000000