Year	Percent
1979-01-01	56.9491359250000
1980-01-01	57.5512073333333
1981-01-01	57.5994405583333
1982-01-01	56.4297136000000
1983-01-01	54.4155554666667
1984-01-01	55.1064665000000
1985-01-01	55.7804712416667
1986-01-01	56.8849308916667
1987-01-01	56.9336737916667
1988-01-01	57.8692916583333
1989-01-01	59.2562727250000
1990-01-01	59.3320012750000
1991-01-01	57.0909602083333
1992-01-01	56.1186174333333
1993-01-01	55.6588285500000
1994-01-01	56.8153598666667
1995-01-01	58.1583642916667
1996-01-01	58.1163124333333
1997-01-01	57.8437542166667
1998-01-01	58.1609246916667
1999-01-01	58.4489791916667
2000-01-01	59.1696383083333
2001-01-01	59.0297465166667
2002-01-01	59.3275571333333
2003-01-01	59.8156571500000
2004-01-01	60.0344997833333
2005-01-01	61.1555340333333
2006-01-01	61.6569675250000
2007-01-01	62.3211109333333
2008-01-01	62.7077672916667
2009-01-01	61.7928169333333
2010-01-01	61.9810874416667
2011-01-01	62.0979256083333
2012-01-01	61.7511064666667
2013-01-01	61.2672786833333
2014-01-01	60.7796862416667
2015-01-01	61.0706958250000
2016-01-01	61.1736338333333
2017-01-01	61.5228371500000