Year	Percent
1991-01-01	40.2210006713867
1992-01-01	40.2260017395020
1993-01-01	40.0909996032715
1994-01-01	40.0349998474121
1995-01-01	40.2669982910156
1996-01-01	40.2760009765625
1997-01-01	40.0919990539551
1998-01-01	40.2540016174316
1999-01-01	40.0530014038086
2000-01-01	40.3860015869141
2001-01-01	40.2560005187988
2002-01-01	40.2840003967285
2003-01-01	40.1500015258789
2004-01-01	40.2459983825684
2005-01-01	40.3930015563965
2006-01-01	38.4760017395020
2007-01-01	36.3559989929199
2008-01-01	34.7159996032715
2009-01-01	33.2709999084473
2010-01-01	30.1849994659424
2011-01-01	27.1000003814697
2012-01-01	20.7460002899170
2013-01-01	20.7329998016357
2014-01-01	20.8269996643066
2015-01-01	20.7169990539551
2016-01-01	21.5189990997314
2017-01-01	22.4619998931885