Year	Percent
1991-01-01	49.3359985351563
1992-01-01	49.5019989013672
1993-01-01	49.4539985656738
1994-01-01	49.2630004882813
1995-01-01	48.8629989624023
1996-01-01	47.9410018920898
1997-01-01	47.2029991149902
1998-01-01	46.7649993896484
1999-01-01	46.6310005187988
2000-01-01	47.6189994812012
2001-01-01	47.2000007629395
2002-01-01	46.8160018920898
2003-01-01	46.9669990539551
2004-01-01	47.1800003051758
2005-01-01	47.3979988098145
2006-01-01	47.3230018615723
2007-01-01	47.5540008544922
2008-01-01	47.7299995422363
2009-01-01	47.4269981384277
2010-01-01	48.2350006103516
2011-01-01	49.1710014343262
2012-01-01	50.5159988403320
2013-01-01	51.3219985961914
2014-01-01	51.6879997253418
2015-01-01	52.5219993591309
2016-01-01	52.7270011901855
2017-01-01	53.0239982604980