Year	Percent
1998-01-01	7.38950152053654
1999-01-01	8.04878246214426
2000-01-01	7.48207492830664
2001-01-01	7.24970032591527
2002-01-01	6.79617101395871
2003-01-01	6.22276333601062
2004-01-01	6.64704173754089
2005-01-01	6.22260444715137
2006-01-01	5.68847357480433
2007-01-01	5.24096565477870
2008-01-01	5.12666208357524
2009-01-01	6.96738989243095
2010-01-01	10.03887677236060
2011-01-01	15.13118239154310
2012-01-01	21.54185143507290
2013-01-01	24.47355181340620
2014-01-01	23.59340285228630
2015-01-01	21.72016484875280
2016-01-01	19.85748327681540
2017-01-01	17.81989394972910