Year	Percent of Total
1960-01-01	62.0344398095726
1961-01-01	61.5096546661456
1962-01-01	60.9285816470888
1963-01-01	60.3831955104676
1964-01-01	60.0090002708019
1965-01-01	59.8743985770608
1966-01-01	59.8914826721618
1967-01-01	60.1119932653091
1968-01-01	60.5128210997166
1969-01-01	61.0144956974450
1970-01-01	61.5537604763699
1971-01-01	62.2789408802810
1972-01-01	62.8898135646033
1973-01-01	63.3972326568794
1974-01-01	63.8617386784303
1975-01-01	64.3276607161929
1976-01-01	64.4967547918504
1977-01-01	64.7776683328884
1978-01-01	65.1105237256921
1979-01-01	65.3816096893551
1980-01-01	65.5247917746303
1981-01-01	65.6036616948454
1982-01-01	65.5767586927266
1983-01-01	65.4806862570013
1984-01-01	65.3676594586722
1985-01-01	65.2486312894492
1986-01-01	64.9108369884545
1987-01-01	64.5491594973305
1988-01-01	64.2197545944402
1989-01-01	63.9601992705316
1990-01-01	63.7924381478402
1991-01-01	63.6269205670963
1992-01-01	63.6205226917480
1993-01-01	63.7609107733825
1994-01-01	64.0218227735036
1995-01-01	64.3879742304939
1996-01-01	64.8003105662039
1997-01-01	65.2518558641901
1998-01-01	65.7653474350643
1999-01-01	66.3834700077386
2000-01-01	67.1223580362140
2001-01-01	67.9126174738771
2002-01-01	68.8029495649109
2003-01-01	69.7521553842296
2004-01-01	70.6872727770221
2005-01-01	71.5577053557749
2006-01-01	72.0356935192401
2007-01-01	72.4526110114955
2008-01-01	72.7974383670928
2009-01-01	73.0877872286403
2010-01-01	73.3369062066882
2011-01-01	73.6087593761466
2012-01-01	73.8954459861212
2013-01-01	74.1663236708380
2014-01-01	74.3375269260792
2015-01-01	74.3347483263567
2016-01-01	73.9568943602436
2017-01-01	73.3965786041313