Year	Percent
1991-01-01	59.5020848357271
1992-01-01	59.4704787187551
1993-01-01	59.3152459090556
1994-01-01	59.1547557564058
1995-01-01	59.1777100738875
1996-01-01	58.9354503415198
1997-01-01	58.7432737429096
1998-01-01	58.6073964892503
1999-01-01	58.4237359004536
2000-01-01	58.1913055909936
2001-01-01	57.9532389582412
2002-01-01	57.8716929411707
2003-01-01	57.7880169680257
2004-01-01	57.5355405241187
2005-01-01	57.4784275738484
2006-01-01	57.3756014092208
2007-01-01	57.2745970427533
2008-01-01	57.1632343134030
2009-01-01	57.1039070231715
2010-01-01	56.9019893879397
2011-01-01	56.7549597266955
2012-01-01	56.6844732462634
2013-01-01	56.5952209010893
2014-01-01	56.5107888500111
2015-01-01	56.4654614191009
2016-01-01	56.4336051701467
2017-01-01	56.4111850985782