Year	Percent of Total
1960-01-01	51.0343656779764
1961-01-01	50.5502046998130
1962-01-01	50.2471017504965
1963-01-01	50.1183418614611
1964-01-01	50.1155751238305
1965-01-01	50.1969732848255
1966-01-01	50.2539033692240
1967-01-01	50.4304560563206
1968-01-01	50.7430954887827
1969-01-01	51.1611723068358
1970-01-01	51.6979952323264
1971-01-01	52.3075444497837
1972-01-01	52.9532030895048
1973-01-01	53.6471158868741
1974-01-01	54.3416697315189
1975-01-01	55.0218419764723
1976-01-01	55.6603605052075
1977-01-01	56.1520859003697
1978-01-01	56.5381013492421
1979-01-01	56.8847639558336
1980-01-01	57.2254335260116
1981-01-01	57.0418904761113
1982-01-01	57.0682862770847
1983-01-01	57.2108535163839
1984-01-01	57.2851111288138
1985-01-01	57.1582582066466
1986-01-01	57.2453371592539
1987-01-01	57.0642720149864
1988-01-01	56.7252308315725
1989-01-01	56.4338131526955
1990-01-01	56.2876318842181
1991-01-01	55.8358208955224
1992-01-01	55.5551097379930
1993-01-01	55.4378689628759
1994-01-01	55.4081725815497
1995-01-01	55.4136112183198
1996-01-01	55.5311949510183
1997-01-01	55.6544946622768
1998-01-01	55.8503985285101
1999-01-01	56.2049514258853
2000-01-01	56.7151624292112
2001-01-01	57.0150713969578
2002-01-01	57.6497257937098
2003-01-01	58.4577310309916
2004-01-01	59.1427182964812
2005-01-01	59.5353371242892
2006-01-01	60.2408232548271
2007-01-01	60.3337105834225
2008-01-01	60.1605038602194
2009-01-01	60.1284702887598
2010-01-01	60.3953162140046
2011-01-01	60.2851245986852
2012-01-01	60.5714124919100
2013-01-01	61.0356106325149
2014-01-01	61.3409621756686
2015-01-01	61.3520510288505
2016-01-01	61.3829275755059
2017-01-01	61.1135930170621