Year	Percent of Total
1960-01-01	48.2735906968403
1961-01-01	47.9838222866111
1962-01-01	47.8118226215038
1963-01-01	47.7299318343677
1964-01-01	47.7140654557163
1965-01-01	47.7620082400774
1966-01-01	47.4829465340498
1967-01-01	47.3572420320968
1968-01-01	47.3804182546500
1969-01-01	47.5564811584089
1970-01-01	47.8801313319310
1971-01-01	48.1231700673335
1972-01-01	48.3119862976807
1973-01-01	48.4557913255001
1974-01-01	48.5624447067782
1975-01-01	48.6620856243141
1976-01-01	50.0918741213845
1977-01-01	51.5608944086992
1978-01-01	53.0876425134940
1979-01-01	54.6131860545392
1980-01-01	56.0324937909514
1981-01-01	57.3379205945090
1982-01-01	58.3234440928270
1983-01-01	59.0626882014783
1984-01-01	59.6733394984496
1985-01-01	60.2115917839933
1986-01-01	60.3716961156058
1987-01-01	60.7140809166593
1988-01-01	61.0997697954220
1989-01-01	61.3574239283891
1990-01-01	61.4245886833942
1991-01-01	61.4357346537706
1992-01-01	61.2884760492285
1993-01-01	61.0602759284623
1994-01-01	60.8795136338571
1995-01-01	60.8170844939647
1996-01-01	60.9540125678835
1997-01-01	61.1750308145120
1998-01-01	61.4717479850940
1999-01-01	61.8098813069723
2000-01-01	62.1632549376575
2001-01-01	62.3328588772135
2002-01-01	62.5299144591383
2003-01-01	62.7444033976885
2004-01-01	62.9773311994814
2005-01-01	63.2377050823135
2006-01-01	63.5743703736018
2007-01-01	63.9422803386273
2008-01-01	64.3298624861205
2009-01-01	64.7171924190243
2010-01-01	65.0859242391699
2011-01-01	65.3862288346824
2012-01-01	65.6652584266316
2013-01-01	65.9226969440041
2014-01-01	66.1592399001328
2015-01-01	66.3786496218420
2016-01-01	66.5057811335893
2017-01-01	66.6321738296989