Year	Percent
1991-01-01	17.8190002441406
1992-01-01	17.8980007171631
1993-01-01	18.0559997558594
1994-01-01	17.7740001678467
1995-01-01	18.1809997558594
1996-01-01	18.0520000457764
1997-01-01	17.7600002288818
1998-01-01	17.9330005645752
1999-01-01	18.1270008087158
2000-01-01	17.8040008544922
2001-01-01	17.8929996490479
2002-01-01	17.8339996337891
2003-01-01	18.0289993286133
2004-01-01	18.0130004882813
2005-01-01	18.1250000000000
2006-01-01	18.2059993743896
2007-01-01	17.8859996795654
2008-01-01	17.8159999847412
2009-01-01	17.7380008697510
2010-01-01	17.9519996643066
2011-01-01	17.9479999542236
2012-01-01	17.9890003204346
2013-01-01	18.0030002593994
2014-01-01	17.9869995117188
2015-01-01	17.8090000152588
2016-01-01	17.8409996032715
2017-01-01	17.9309997558594