Year	Percent
1979-01-01	68.7331191916666
1980-01-01	69.4609864833334
1981-01-01	69.4216769416667
1982-01-01	69.1658588916667
1983-01-01	68.8683678666666
1984-01-01	69.0959965083333
1985-01-01	69.5176196166667
1986-01-01	70.9312646416666
1987-01-01	71.1304248250000
1988-01-01	71.7192428750000
1989-01-01	72.7310526583333
1990-01-01	73.5087223250000
1991-01-01	72.9813954250000
1992-01-01	72.8234524750000
1993-01-01	72.5858932416666
1994-01-01	73.1917602500000
1995-01-01	73.9634665500000
1996-01-01	74.0305373000000
1997-01-01	73.5928607500000
1998-01-01	73.5155741333333
1999-01-01	73.3368948500000
2000-01-01	73.7928383583333
2001-01-01	74.0554282750000
2002-01-01	74.1478639250000
2003-01-01	74.4892949750000
2004-01-01	74.3684063333334
2005-01-01	75.3966378000000
2006-01-01	75.8017008083334
2007-01-01	76.1914274750000
2008-01-01	76.5032430000000
2009-01-01	76.3861349416667
2010-01-01	76.4345842166667
2011-01-01	76.6434637083334
2012-01-01	76.4280329833333
2013-01-01	76.4025235083333
2014-01-01	76.3077044416667
2015-01-01	76.9423146833334
2016-01-01	76.9468094916667
2017-01-01	77.4439504833334