Year	Percent
1991-01-01	58.0760002136230
1992-01-01	56.1829986572266
1993-01-01	54.6539993286133
1994-01-01	51.7980003356934
1995-01-01	52.0699996948242
1996-01-01	53.3670005798340
1997-01-01	52.5519981384277
1998-01-01	52.0489997863770
1999-01-01	49.8899993896484
2000-01-01	48.3610000610352
2001-01-01	48.7389984130859
2002-01-01	48.6160011291504
2003-01-01	49.9220008850098
2004-01-01	49.0130004882813
2005-01-01	49.8800010681152
2006-01-01	51.1990013122559
2007-01-01	52.2099990844727
2008-01-01	53.5589981079102
2009-01-01	51.6590003967285
2010-01-01	50.3330001831055
2011-01-01	50.7239990234375
2012-01-01	50.8660011291504
2013-01-01	50.7799987792969
2014-01-01	51.4650001525879
2015-01-01	52.7589988708496
2016-01-01	54.2459983825684
2017-01-01	54.9329986572266