Year	Percent
1991-01-01	28.4799995422363
1992-01-01	28.1079998016357
1993-01-01	30.0590000152588
1994-01-01	31.7369995117188
1995-01-01	33.4729995727539
1996-01-01	34.8019981384277
1997-01-01	34.6860008239746
1998-01-01	33.9090003967285
1999-01-01	33.0610008239746
2000-01-01	31.5170001983643
2001-01-01	27.8209991455078
2002-01-01	27.1660003662109
2003-01-01	26.9629993438721
2004-01-01	24.4080009460449
2005-01-01	24.0970001220703
2006-01-01	21.7950000762939
2007-01-01	20.3630008697510
2008-01-01	21.1800003051758
2009-01-01	25.3829994201660
2010-01-01	27.9580001831055
2011-01-01	29.2940006256104
2012-01-01	35.4930000305176
2013-01-01	40.2560005187988
2014-01-01	42.8670005798340
2015-01-01	40.4869995117188
2016-01-01	37.8499984741211
2017-01-01	34.7260017395020