Year	Percent of Total
1960-01-01	55.8270863084144
1961-01-01	55.3201379324821
1962-01-01	54.7999408165670
1963-01-01	54.3377670794374
1964-01-01	54.0327748158421
1965-01-01	53.9144920011397
1966-01-01	53.7283050602113
1967-01-01	53.7131285763146
1968-01-01	53.8180180320721
1969-01-01	53.9700092156313
1970-01-01	54.1309150364133
1971-01-01	54.1256433629843
1972-01-01	54.1846314094320
1973-01-01	54.2834511356815
1974-01-01	54.4061689417438
1975-01-01	54.5473588608722
1976-01-01	54.6007638876702
1977-01-01	54.6839032370714
1978-01-01	54.7976216286090
1979-01-01	54.9467975115386
1980-01-01	55.1317044630173
1981-01-01	55.2254319310422
1982-01-01	55.3584515905097
1983-01-01	55.5394774427199
1984-01-01	55.7866529958358
1985-01-01	56.1109986337221
1986-01-01	56.3315856867917
1987-01-01	56.6748051966992
1988-01-01	57.1034167805197
1989-01-01	57.5705921464880
1990-01-01	58.0562321159349
1991-01-01	58.4986543872279
1992-01-01	58.9304811039363
1993-01-01	59.3760052469359
1994-01-01	59.8653458051106
1995-01-01	60.4029942139506
1996-01-01	60.9208369954224
1997-01-01	61.4623883222405
1998-01-01	62.0123627847772
1999-01-01	62.5433187741569
2000-01-01	63.0374005146103
2001-01-01	63.3305541731004
2002-01-01	63.5920027526388
2003-01-01	63.8241672516898
2004-01-01	64.0452149862294
2005-01-01	64.2743314129061
2006-01-01	64.3668630001830
2007-01-01	64.5182850111851
2008-01-01	64.7125414048155
2009-01-01	64.9185121732249
2010-01-01	65.1202482754969
2011-01-01	65.4845186236212
2012-01-01	65.8134796193362
2013-01-01	66.1280620995924
2014-01-01	66.4567618994942
2015-01-01	66.8042327341622
2016-01-01	67.1156761502169
2017-01-01	67.4372630823830