Year	Percent
1979-01-01	67.9634360750000
1980-01-01	69.2196084333333
1981-01-01	70.7015157583333
1982-01-01	67.6787679416667
1983-01-01	61.7589085583333
1984-01-01	62.5023682083333
1985-01-01	63.8167209416667
1986-01-01	64.3421254833333
1987-01-01	63.5719997333333
1988-01-01	64.6710239250000
1989-01-01	67.3627186916666
1990-01-01	65.3150639000000
1991-01-01	59.0876182166667
1992-01-01	57.2176433500000
1993-01-01	57.5253722750000
1994-01-01	60.2356599416667
1995-01-01	62.2195164333333
1996-01-01	61.6771161750000
1997-01-01	60.2525863250000
1998-01-01	61.0332016250000
1999-01-01	61.9559716416667
2000-01-01	62.5967764916667
2001-01-01	61.6925388083333
2002-01-01	61.7916136750000
2003-01-01	62.3967620083333
2004-01-01	62.7428077583333
2005-01-01	64.1759583416667
2006-01-01	64.4639481083334
2007-01-01	64.9860989333333
2008-01-01	65.4845788750000
2009-01-01	61.6239889666667
2010-01-01	61.2927179666667
2011-01-01	60.5772368833333
2012-01-01	59.7318878750000
2013-01-01	58.5865473333333
2014-01-01	57.4580263250000
2015-01-01	58.1678634500000
2016-01-01	57.9136038083333
2017-01-01	58.1764950166667