Year	Percent
1991-01-01	56.4840011596680
1992-01-01	56.3040008544922
1993-01-01	54.2280006408691
1994-01-01	53.4430007934570
1995-01-01	49.0870018005371
1996-01-01	50.3470001220703
1997-01-01	52.1310005187988
1998-01-01	53.7340011596680
1999-01-01	52.8870010375977
2000-01-01	52.4210014343262
2001-01-01	50.9729995727539
2002-01-01	49.2859992980957
2003-01-01	52.3320007324219
2004-01-01	53.9350013732910
2005-01-01	54.9080009460449
2006-01-01	56.0530014038086
2007-01-01	56.3769989013672
2008-01-01	56.0870018005371
2009-01-01	55.9389991760254
2010-01-01	55.1139984130859
2011-01-01	56.4700012207031
2012-01-01	56.3100013732910
2013-01-01	56.1139984130859
2014-01-01	55.5089988708496
2015-01-01	55.7089996337891
2016-01-01	54.7490005493164
2017-01-01	54.7509994506836