Year	Percent
1991-01-01	73.0789719590609
1992-01-01	73.4134460235771
1993-01-01	73.3834473854308
1994-01-01	73.2874910754846
1995-01-01	73.0467111354105
1996-01-01	72.9054078028875
1997-01-01	72.6465167965963
1998-01-01	72.3061543178125
1999-01-01	72.0591710505680
2000-01-01	71.8990568014401
2001-01-01	71.4221532667608
2002-01-01	70.9192907637174
2003-01-01	70.3906933819242
2004-01-01	69.7801644143079
2005-01-01	69.3023657936104
2006-01-01	68.9393817600603
2007-01-01	68.6921431986879
2008-01-01	68.1339900609164
2009-01-01	67.9556020536099
2010-01-01	67.7424780797800
2011-01-01	67.6279570890342
2012-01-01	67.4434835981200
2013-01-01	67.1982216417120
2014-01-01	67.0050394976596
2015-01-01	66.5297949138253
2016-01-01	66.3083570435745
2017-01-01	65.9933347253741