Year	Percent of Total
1960-01-01	51.8805190318889
1961-01-01	53.2796454223471
1962-01-01	54.8083078455082
1963-01-01	56.3424812449230
1964-01-01	57.8045030282468
1965-01-01	59.1791809100703
1966-01-01	60.5043587714433
1967-01-01	61.6180123676468
1968-01-01	62.4894920139306
1969-01-01	63.1316848199392
1970-01-01	63.5166179049592
1971-01-01	66.1864078505638
1972-01-01	68.2398725808390
1973-01-01	69.5914133352133
1974-01-01	70.2584414592544
1975-01-01	70.3473059077363
1976-01-01	71.1470716894688
1977-01-01	71.5322603282642
1978-01-01	71.4245149965621
1979-01-01	71.0197050544095
1980-01-01	70.5556685444136
1981-01-01	69.8520831474708
1982-01-01	69.1472790016351
1983-01-01	68.3956075527110
1984-01-01	67.6192549287891
1985-01-01	66.8840560956744
1986-01-01	66.7581159855402
1987-01-01	66.8369301821341
1988-01-01	67.0602814628629
1989-01-01	67.4099666124349
1990-01-01	67.8807466398305
1991-01-01	68.6427488774260
1992-01-01	69.4143548548647
1993-01-01	70.1874372849568
1994-01-01	70.9556376428595
1995-01-01	71.6917944152694
1996-01-01	72.0547486989600
1997-01-01	72.4381391180032
1998-01-01	72.6818749570582
1999-01-01	72.7991320417033
2000-01-01	72.9229062497524
2001-01-01	75.0635291542595
2002-01-01	76.9558728934955
2003-01-01	78.5198127598257
2004-01-01	79.7457442407908
2005-01-01	80.6664480140241
2006-01-01	82.4429343430181
2007-01-01	83.7910301126708
2008-01-01	84.7128589824779
2009-01-01	85.3509205698169
2010-01-01	85.8724018472958
2011-01-01	85.6406504486897
2012-01-01	85.5253547207091
2013-01-01	85.4376226854579
2014-01-01	85.3226819442949
2015-01-01	85.1916071809735
2016-01-01	85.0281004210317
2017-01-01	84.9605617785683