Year	Percent
1991-01-01	71.4669699419182
1992-01-01	71.7701455842297
1993-01-01	71.7084307925414
1994-01-01	71.6413580145316
1995-01-01	71.4387795953826
1996-01-01	71.3275369074117
1997-01-01	71.1234732478241
1998-01-01	70.6596437412039
1999-01-01	70.3966463292799
2000-01-01	70.2895241355034
2001-01-01	69.8407181379382
2002-01-01	69.3722188783904
2003-01-01	68.8951810165415
2004-01-01	68.3958384121327
2005-01-01	68.0126278019154
2006-01-01	67.7241242214551
2007-01-01	67.5524562711241
2008-01-01	67.0440971989763
2009-01-01	66.7804618190108
2010-01-01	66.5893874887097
2011-01-01	66.5015124048588
2012-01-01	66.3470740919782
2013-01-01	66.1695097329198
2014-01-01	66.0475785726376
2015-01-01	65.6617098009395
2016-01-01	65.5041200525268
2017-01-01	65.2218583851288