Year	Percent
1968-01-01	64.1271587193476
1969-01-01	64.0300119971803
1970-01-01	63.3243792108129
1971-01-01	63.5669140071248
1972-01-01	62.1530596716447
1973-01-01	62.9049920004056
1974-01-01	62.1072821220040
1975-01-01	61.3216558316846
1976-01-01	61.2139485428822
1977-01-01	60.7232387864896
1978-01-01	60.9961994892839
1979-01-01	61.2542438714612
1980-01-01	61.4919217241126
1981-01-01	60.9231894492608
1982-01-01	61.0953013556926
1983-01-01	61.5183053646602
1984-01-01	60.6404594918401
1985-01-01	60.7871166274966
1986-01-01	60.3829303818537
1987-01-01	60.5719550603838
1988-01-01	60.9640962999125
1989-01-01	61.9597154162683
1990-01-01	63.1941540579804
1991-01-01	64.5862212974672
1992-01-01	64.6978992166085
1993-01-01	64.5638118756006
1994-01-01	63.7737783181251
1995-01-01	63.8151429071338
1996-01-01	63.6911079040096
1997-01-01	64.2102004463473
1998-01-01	63.7396486803557
1999-01-01	63.5445819843261
2000-01-01	62.8227329054761
2001-01-01	62.0155754509916
2002-01-01	61.6924764918575
2003-01-01	62.1668509414366
2004-01-01	63.1165024573219
2005-01-01	63.8642372177885
2006-01-01	64.7452330961023
2007-01-01	66.1883750394229
2008-01-01	66.4740240557408
2009-01-01	65.7217086890580
2010-01-01	65.5226594433987
2011-01-01	65.8839318187717
2012-01-01	65.4834815653385
2013-01-01	66.9264231724055
2014-01-01	68.7220229417824
2015-01-01	70.1418876059270
2016-01-01	71.5620265312482
2017-01-01	73.4422238138234