Year	Percent
1991-01-01	58.8699989318848
1992-01-01	56.8079986572266
1993-01-01	55.7840003967285
1994-01-01	54.9690017700195
1995-01-01	54.3260002136230
1996-01-01	54.4420013427734
1997-01-01	55.4389991760254
1998-01-01	57.6780014038086
1999-01-01	57.7169990539551
2000-01-01	58.3919982910156
2001-01-01	59.0120010375977
2002-01-01	59.1650009155273
2003-01-01	58.1419982910156
2004-01-01	57.6570014953613
2005-01-01	57.2680015563965
2006-01-01	57.4160003662109
2007-01-01	57.3149986267090
2008-01-01	57.3530006408691
2009-01-01	55.4749984741211
2010-01-01	54.4729995727539
2011-01-01	52.7169990539551
2012-01-01	50.6959991455078
2013-01-01	49.6250000000000
2014-01-01	50.6139984130859
2015-01-01	51.3390007019043
2016-01-01	52.0649986267090
2017-01-01	53.0340003967285