Year	Percent
1968-01-01	53.4882814499313
1969-01-01	53.0059063318991
1970-01-01	52.8745402734132
1971-01-01	51.9145661747612
1972-01-01	50.9621923879805
1973-01-01	51.5246524923563
1974-01-01	49.8731459808071
1975-01-01	48.9865511521722
1976-01-01	49.1751297776078
1977-01-01	50.2053303414335
1978-01-01	50.9731856603048
1979-01-01	51.4385994429091
1980-01-01	51.6197191023337
1981-01-01	51.7513813360330
1982-01-01	52.1771115155920
1983-01-01	53.1963262015029
1984-01-01	53.1669970305629
1985-01-01	53.2858887123235
1986-01-01	53.3584288861348
1987-01-01	53.5237818064271
1988-01-01	54.0770233226982
1989-01-01	55.0956966460899
1990-01-01	56.0375083355190
1991-01-01	56.8425159412203
1992-01-01	57.0614992603509
1993-01-01	56.6713128291779
1994-01-01	56.5889605710398
1995-01-01	56.5125517388250
1996-01-01	56.8593323282830
1997-01-01	57.5280234841079
1998-01-01	57.2884090712568
1999-01-01	56.7825155013188
2000-01-01	56.8297036731042
2001-01-01	57.0612533988584
2002-01-01	56.5939431516882
2003-01-01	56.8858058632860
2004-01-01	57.4522134753528
2005-01-01	58.1540696288080
2006-01-01	58.8866907792989
2007-01-01	59.5731397472143
2008-01-01	59.8791948182160
2009-01-01	59.8705761138033
2010-01-01	60.2102490593342
2011-01-01	60.8483730303488
2012-01-01	60.7270224306828
2013-01-01	62.5333857338468
2014-01-01	63.7354735597279
2015-01-01	64.6992407500250
2016-01-01	66.1182484830189
2017-01-01	67.4834175038321