Year	Percent
1991-01-01	55.2138231860510
1992-01-01	54.7104458470981
1993-01-01	53.4605888262619
1994-01-01	52.6699237664982
1995-01-01	52.3940431555677
1996-01-01	51.9572345790800
1997-01-01	51.4326202278142
1998-01-01	51.2009527948395
1999-01-01	51.7376815653151
2000-01-01	52.1450255160677
2001-01-01	52.1670492902927
2002-01-01	52.1401952474468
2003-01-01	52.0117203792305
2004-01-01	51.9908750729730
2005-01-01	52.4012275064555
2006-01-01	52.8179258248902
2007-01-01	53.5225366158309
2008-01-01	53.8067471830652
2009-01-01	52.7825349681259
2010-01-01	52.7963087706315
2011-01-01	53.0636539814670
2012-01-01	53.0660226421246
2013-01-01	53.0170722402259
2014-01-01	53.1781069680526
2015-01-01	53.5030872476476
2016-01-01	53.9094756441028
2017-01-01	54.0827697682498