Year	Percent of Total
1960-01-01	54.4345670319354
1961-01-01	54.0684500860075
1962-01-01	53.6950031191660
1963-01-01	53.3531896071228
1964-01-01	53.1114513886742
1965-01-01	53.0101654690487
1966-01-01	52.9543558452293
1967-01-01	53.0629766552442
1968-01-01	53.2930955307832
1969-01-01	53.5822824057118
1970-01-01	53.8967766174803
1971-01-01	54.2774751536647
1972-01-01	54.6430897613144
1973-01-01	55.0286361292679
1974-01-01	55.4829140842998
1975-01-01	56.0185283106665
1976-01-01	56.4862908304712
1977-01-01	57.0504378300406
1978-01-01	57.6584559752707
1979-01-01	58.2369551526376
1980-01-01	58.7498913748457
1981-01-01	59.2083438591847
1982-01-01	59.6086739154916
1983-01-01	59.9645609127342
1984-01-01	60.2981397798174
1985-01-01	60.6127886023922
1986-01-01	60.8766109384161
1987-01-01	61.1063980295617
1988-01-01	61.3126969187696
1989-01-01	61.5303215828594
1990-01-01	61.8015062834951
1991-01-01	61.5305588791216
1992-01-01	61.3074112807340
1993-01-01	61.1469587090225
1994-01-01	61.0223540443769
1995-01-01	60.8998318492463
1996-01-01	61.2897884632052
1997-01-01	61.6360727193723
1998-01-01	61.9530382352496
1999-01-01	62.2826405133433
2000-01-01	62.6621972664696
2001-01-01	63.0644361659335
2002-01-01	63.5138692201964
2003-01-01	64.0031115346970
2004-01-01	64.5069142186240
2005-01-01	65.0104784424679
2006-01-01	65.5245944201857
2007-01-01	65.9537479161892
2008-01-01	66.3168598208815
2009-01-01	66.6197489734645
2010-01-01	66.8606796405404
2011-01-01	67.5208146900612
2012-01-01	68.1105971529832
2013-01-01	68.6455670443559
2014-01-01	69.1030976367574
2015-01-01	69.4364209304935
2016-01-01	69.4436888572377
2017-01-01	69.4157744881129