Year	Percent
1991-01-01	13.9940004348755
1992-01-01	12.6990003585815
1993-01-01	13.9779996871948
1994-01-01	13.5850000381470
1995-01-01	12.8710002899170
1996-01-01	12.9169998168945
1997-01-01	13.8330001831055
1998-01-01	15.1450004577637
1999-01-01	16.6509990692139
2000-01-01	17.4009990692139
2001-01-01	18.7859992980957
2002-01-01	20.0860004425049
2003-01-01	20.1679992675781
2004-01-01	11.6920003890991
2005-01-01	11.6660003662109
2006-01-01	16.8379993438721
2007-01-01	21.9099998474121
2008-01-01	23.1720008850098
2009-01-01	22.8829994201660
2010-01-01	23.6280002593994
2011-01-01	24.2099990844727
2012-01-01	24.3920001983643
2013-01-01	20.7040004730225
2014-01-01	18.3190002441406
2015-01-01	18.1730003356934
2016-01-01	18.5300006866455
2017-01-01	18.7590007781982