Year	Percent
1991-01-01	56.4018622736671
1992-01-01	56.6601082889277
1993-01-01	57.0707164927724
1994-01-01	57.1110879896123
1995-01-01	56.6956334696088
1996-01-01	56.7147461354371
1997-01-01	57.4615474205208
1998-01-01	57.4494212692729
1999-01-01	56.9749581890721
2000-01-01	57.0174442575197
2001-01-01	57.4581420777461
2002-01-01	57.5760065154931
2003-01-01	57.8334814027084
2004-01-01	58.9006340933594
2005-01-01	59.4523598292061
2006-01-01	60.3329987413080
2007-01-01	60.6263187993026
2008-01-01	60.7587003213265
2009-01-01	60.3244201842391
2010-01-01	60.2666836062957
2011-01-01	60.2895351579950
2012-01-01	60.4453132237014
2013-01-01	60.3126151728884
2014-01-01	60.2371837789237
2015-01-01	59.9998347802994
2016-01-01	59.1634006553387
2017-01-01	58.8260587431298