Year	Percent
1968-01-01	56.1744965282137
1969-01-01	55.6151059469533
1970-01-01	55.2050863404051
1971-01-01	53.8903987129619
1972-01-01	53.5971791912371
1973-01-01	54.4583764781173
1974-01-01	53.1688546252087
1975-01-01	52.5052949361240
1976-01-01	53.0435971119194
1977-01-01	54.4479635537244
1978-01-01	55.6607620045314
1979-01-01	56.4318859287910
1980-01-01	56.8645306437182
1981-01-01	57.3664850834265
1982-01-01	58.3239350235590
1983-01-01	59.7901057503760
1984-01-01	60.3229391358137
1985-01-01	60.7464983633078
1986-01-01	61.2069247215110
1987-01-01	61.7455572746220
1988-01-01	62.5538990186828
1989-01-01	63.6256911512796
1990-01-01	64.5628754327078
1991-01-01	65.3622939989297
1992-01-01	65.5995361961025
1993-01-01	65.2603600560198
1994-01-01	65.3316066020109
1995-01-01	65.2918153332050
1996-01-01	65.8198444296404
1997-01-01	66.7481340598810
1998-01-01	66.6975422982009
1999-01-01	66.5403391011068
2000-01-01	66.5771625978440
2001-01-01	67.3249923042756
2002-01-01	67.4242389167061
2003-01-01	67.8204233394576
2004-01-01	68.1778475194074
2005-01-01	68.8461296308563
2006-01-01	69.4091039845844
2007-01-01	70.1672541480977
2008-01-01	70.5256552998213
2009-01-01	71.3675991974671
2010-01-01	71.7386667134390
2011-01-01	72.2273302465717
2012-01-01	72.2318636628259
2013-01-01	73.7447193253716
2014-01-01	74.6624234688268
2015-01-01	75.3349822754722
2016-01-01	76.3473223176940
2017-01-01	77.5023502431160