Year	Percent
1991-01-01	24.4510002136230
1992-01-01	24.8269996643066
1993-01-01	24.4249992370605
1994-01-01	23.9720001220703
1995-01-01	20.9549999237061
1996-01-01	20.3209991455078
1997-01-01	17.1459999084473
1998-01-01	16.6970005035400
1999-01-01	17.1030006408691
2000-01-01	17.5849990844727
2001-01-01	17.4120006561279
2002-01-01	22.0079994201660
2003-01-01	19.3320007324219
2004-01-01	22.1949996948242
2005-01-01	20.1480007171631
2006-01-01	21.3980007171631
2007-01-01	20.1940002441406
2008-01-01	18.7380008697510
2009-01-01	20.9540004730225
2010-01-01	21.8330001831055
2011-01-01	23.6730003356934
2012-01-01	22.4150009155273
2013-01-01	23.6240005493164
2014-01-01	23.8999996185303
2015-01-01	21.5359992980957
2016-01-01	20.5209999084473
2017-01-01	18.4659996032715