Year	Percent
1991-01-01	58.8004894868158
1992-01-01	58.7876105851403
1993-01-01	57.3899985158948
1994-01-01	56.2148556218965
1995-01-01	55.4650890611718
1996-01-01	54.4373834476607
1997-01-01	53.0316743098609
1998-01-01	51.9836905412306
1999-01-01	52.7045763366767
2000-01-01	53.1338361182085
2001-01-01	52.8309004594717
2002-01-01	52.7463825736487
2003-01-01	52.3328029994572
2004-01-01	52.3357609382243
2005-01-01	52.6569107107959
2006-01-01	52.8715100244116
2007-01-01	53.5776953240429
2008-01-01	53.8328749094730
2009-01-01	52.9585965701790
2010-01-01	53.5477705445607
2011-01-01	54.2230503491950
2012-01-01	54.5996600615313
2013-01-01	54.8021519438769
2014-01-01	54.7229655718207
2015-01-01	54.8999909678803
2016-01-01	55.0822308505676
2017-01-01	54.9917201153297