Year	Percent
1991-01-01	62.6290016174316
1992-01-01	62.7410011291504
1993-01-01	62.6049995422363
1994-01-01	62.4819984436035
1995-01-01	62.4319992065430
1996-01-01	62.3419990539551
1997-01-01	62.2939987182617
1998-01-01	62.1759986877441
1999-01-01	62.1389999389648
2000-01-01	62.1259994506836
2001-01-01	62.2700004577637
2002-01-01	62.1240005493164
2003-01-01	62.1090011596680
2004-01-01	63.5639991760254
2005-01-01	62.7130012512207
2006-01-01	61.8670005798340
2007-01-01	61.0369987487793
2008-01-01	60.2130012512207
2009-01-01	59.3909988403320
2010-01-01	58.5670013427734
2011-01-01	57.7379989624023
2012-01-01	56.9090003967285
2013-01-01	56.0789985656738
2014-01-01	55.2900009155273
2015-01-01	55.4599990844727
2016-01-01	55.3810005187988
2017-01-01	55.3199996948242