Year	Percent
1991-01-01	81.7429962158203
1992-01-01	81.7990036010742
1993-01-01	81.9520034790039
1994-01-01	82.2429962158203
1995-01-01	82.2720031738281
1996-01-01	82.2959976196289
1997-01-01	82.8489990234375
1998-01-01	83.4049987792969
1999-01-01	84.4410018920898
2000-01-01	84.2229995727539
2001-01-01	84.0090026855469
2002-01-01	83.7350006103516
2003-01-01	83.5299987792969
2004-01-01	83.2679977416992
2005-01-01	82.9489974975586
2006-01-01	82.6220016479492
2007-01-01	82.2839965820313
2008-01-01	81.9120025634766
2009-01-01	81.6370010375977
2010-01-01	81.3970031738281
2011-01-01	81.2959976196289
2012-01-01	81.2429962158203
2013-01-01	81.1179962158203
2014-01-01	81.5240020751953
2015-01-01	81.5199966430664
2016-01-01	81.7070007324219
2017-01-01	81.9020004272461