Year	Percent
1991-01-01	69.1125438737986
1992-01-01	69.1049407566592
1993-01-01	68.9743933020377
1994-01-01	68.9016578840027
1995-01-01	68.7811259577274
1996-01-01	68.6620595751835
1997-01-01	68.5034124019067
1998-01-01	68.3720120557304
1999-01-01	68.2682301517981
2000-01-01	68.2806367327018
2001-01-01	68.3069720793885
2002-01-01	68.5120334066697
2003-01-01	68.5733926275187
2004-01-01	68.5626936265871
2005-01-01	68.6167562009614
2006-01-01	68.4676922744393
2007-01-01	68.3637313774095
2008-01-01	68.2671450816297
2009-01-01	68.3073506768026
2010-01-01	68.1727412195833
2011-01-01	68.1201202100437
2012-01-01	68.2344970058346
2013-01-01	68.3237224502805
2014-01-01	68.3296669204962
2015-01-01	68.2800792574408
2016-01-01	68.2551669513191
2017-01-01	68.2952672857941