Year	Percent
1991-01-01	58.0470008850098
1992-01-01	58.6059989929199
1993-01-01	58.2330017089844
1994-01-01	59.2039985656738
1995-01-01	58.1520004272461
1996-01-01	57.8019981384277
1997-01-01	56.9539985656738
1998-01-01	56.7929992675781
1999-01-01	56.4280014038086
2000-01-01	56.3460006713867
2001-01-01	56.5429992675781
2002-01-01	56.7190017700195
2003-01-01	58.1829986572266
2004-01-01	58.3450012207031
2005-01-01	58.7729988098145
2006-01-01	59.7290000915527
2007-01-01	60.0180015563965
2008-01-01	59.3860015869141
2009-01-01	58.7700004577637
2010-01-01	58.1800003051758
2011-01-01	58.0410003662109
2012-01-01	57.2970008850098
2013-01-01	56.4939994812012
2014-01-01	57.5750007629395
2015-01-01	57.8009986877441
2016-01-01	58.1809997558594
2017-01-01	58.8610000610352