Year	Percent
1991-01-01	44.8810005187988
1992-01-01	44.4370002746582
1993-01-01	44.6619987487793
1994-01-01	45.8279991149902
1995-01-01	47.3950004577637
1996-01-01	48.3370018005371
1997-01-01	49.6580009460449
1998-01-01	52.6129989624023
1999-01-01	55.0719985961914
2000-01-01	56.7890014648438
2001-01-01	57.3269996643066
2002-01-01	57.3740005493164
2003-01-01	57.4729995727539
2004-01-01	57.9469985961914
2005-01-01	59.7999992370605
2006-01-01	60.4659996032715
2007-01-01	60.9169998168945
2008-01-01	59.4640007019043
2009-01-01	54.6980018615723
2010-01-01	52.6860008239746
2011-01-01	51.7220001220703
2012-01-01	51.4430007934570
2013-01-01	52.6580009460449
2014-01-01	53.4860000610352
2015-01-01	54.5730018615723
2016-01-01	55.6199989318848
2017-01-01	56.1520004272461