Year	Percent of Total
1960-01-01	52.3127652181136
1961-01-01	51.5570100956316
1962-01-01	50.7313885538539
1963-01-01	49.9495927952568
1964-01-01	49.3707071775695
1965-01-01	49.0640832932979
1966-01-01	48.7199111591332
1967-01-01	48.5966874153850
1968-01-01	48.6435651904173
1969-01-01	48.7769107491194
1970-01-01	48.9625005187497
1971-01-01	49.1567973912104
1972-01-01	49.4383978247863
1973-01-01	49.7980399626609
1974-01-01	50.2298735876126
1975-01-01	50.7205806344277
1976-01-01	51.2372579411045
1977-01-01	51.7885008926072
1978-01-01	52.3538184559692
1979-01-01	52.9048990431373
1980-01-01	53.4207029654123
1981-01-01	53.7659980807934
1982-01-01	54.0947920850816
1983-01-01	54.4050672917233
1984-01-01	54.7088182429946
1985-01-01	55.0207619556066
1986-01-01	55.2138068492636
1987-01-01	55.4804018390514
1988-01-01	55.7904324462833
1989-01-01	56.0999584336407
1990-01-01	56.3921351609638
1991-01-01	56.7555642841643
1992-01-01	57.0478817551244
1993-01-01	57.3340889463319
1994-01-01	57.7042873286912
1995-01-01	58.1969048316927
1996-01-01	58.6611845340760
1997-01-01	59.2696782756468
1998-01-01	59.9586168902842
1999-01-01	60.6226107581053
2000-01-01	61.2070259085899
2001-01-01	61.8163965853823
2002-01-01	62.2932256740632
2003-01-01	62.6876273060086
2004-01-01	63.0772962315045
2005-01-01	63.4940911311432
2006-01-01	63.8752793790967
2007-01-01	64.3017758249959
2008-01-01	64.7325912658080
2009-01-01	65.0984996919496
2010-01-01	65.3634247515068
2011-01-01	65.6375762455034
2012-01-01	65.8041994565934
2013-01-01	65.8833708516975
2014-01-01	65.9212685604050
2015-01-01	65.9443946184218
2016-01-01	65.8717832174394
2017-01-01	65.8380736427233