Year	Percent of Total
1960-01-01	59.0587627501537
1961-01-01	58.4267326270113
1962-01-01	58.9498212220782
1963-01-01	59.9672387345439
1964-01-01	60.4879869348212
1965-01-01	60.0575491979494
1966-01-01	60.0844511375634
1967-01-01	58.8176811775271
1968-01-01	57.0140357276005
1969-01-01	55.6918572776861
1970-01-01	55.2340046077833
1971-01-01	54.5699958830539
1972-01-01	54.8571056205410
1973-01-01	55.6955076557951
1974-01-01	56.5004195691621
1975-01-01	57.0242596809534
1976-01-01	57.6446053596956
1977-01-01	58.1176237207365
1978-01-01	58.5375937434822
1979-01-01	59.0786163992735
1980-01-01	59.7990858589732
1981-01-01	60.9035019003194
1982-01-01	61.8388950945783
1983-01-01	62.7254933186375
1984-01-01	63.6992743141552
1985-01-01	64.7950033792020
1986-01-01	65.3917578592870
1987-01-01	66.3273789925538
1988-01-01	67.3597190384996
1989-01-01	68.1450382882055
1990-01-01	68.5345389609666
1991-01-01	68.8532811882101
1992-01-01	68.7493540268889
1993-01-01	68.3951638106458
1994-01-01	68.0828216466211
1995-01-01	67.9549803979902
1996-01-01	67.7867658324209
1997-01-01	67.8204714814952
1998-01-01	67.9827686821548
1999-01-01	68.1238440021846
2000-01-01	68.1669496043778
2001-01-01	68.1473607123697
2002-01-01	68.0508852137114
2003-01-01	67.9255000522547
2004-01-01	67.8523751324196
2005-01-01	67.8694555639609
2006-01-01	67.8610829755601
2007-01-01	67.9592017432011
2008-01-01	68.1317999900227
2009-01-01	68.3184018850329
2010-01-01	68.4851033883563
2011-01-01	68.6123636241259
2012-01-01	68.6848501132653
2013-01-01	68.7576262780369
2014-01-01	68.9168730361159
2015-01-01	69.1961077197331
2016-01-01	69.4828532257569
2017-01-01	69.8919676049926