Year	Percent
1991-01-01	56.4924190532781
1992-01-01	56.0405051124199
1993-01-01	55.4951601063961
1994-01-01	55.5054713902977
1995-01-01	55.5643701642238
1996-01-01	55.6533662807732
1997-01-01	55.9572085205395
1998-01-01	56.0070148929292
1999-01-01	56.1321248243781
2000-01-01	56.4034203673506
2001-01-01	56.1908636255912
2002-01-01	55.8226893201098
2003-01-01	55.8121866854140
2004-01-01	55.9465813988670
2005-01-01	56.3392462557720
2006-01-01	56.8108815461938
2007-01-01	57.2336920803625
2008-01-01	57.1847626815010
2009-01-01	55.7348753097681
2010-01-01	55.3892731337290
2011-01-01	55.4778250112399
2012-01-01	55.5344656991864
2013-01-01	55.5620922604341
2014-01-01	55.9071331024017
2015-01-01	56.2839143053467
2016-01-01	56.6545749920799
2017-01-01	56.8321183924707