Year	Percent of Total
1960-01-01	50.3856736824624
1961-01-01	50.1770930523901
1962-01-01	50.0020428371814
1963-01-01	49.8813766562879
1964-01-01	49.8390698426335
1965-01-01	49.8806245623027
1966-01-01	49.8621146850066
1967-01-01	49.9463920973134
1968-01-01	50.1151372019567
1969-01-01	50.3577529978323
1970-01-01	50.6767057027457
1971-01-01	50.9717014684159
1972-01-01	51.3979878776348
1973-01-01	51.9116261105196
1974-01-01	52.4485665309031
1975-01-01	52.9714759554813
1976-01-01	53.5920405019767
1977-01-01	54.0963763659603
1978-01-01	54.5551371159625
1979-01-01	55.0646076391727
1980-01-01	55.6557706243083
1981-01-01	56.0863583583742
1982-01-01	56.6427472310245
1983-01-01	57.2419550394525
1984-01-01	57.7708873707969
1985-01-01	58.1853396693530
1986-01-01	58.5153459879224
1987-01-01	58.7715412464143
1988-01-01	58.9841286881320
1989-01-01	59.2103827798610
1990-01-01	59.4812492513838
1991-01-01	59.7929487513248
1992-01-01	60.1129085718081
1993-01-01	60.4579870992725
1994-01-01	60.8440004011565
1995-01-01	61.2764812071756
1996-01-01	61.6991288978186
1997-01-01	62.1903361307245
1998-01-01	62.7200645194474
1999-01-01	63.2405976009762
2000-01-01	63.7257072685800
2001-01-01	64.2211677310074
2002-01-01	64.6534267095036
2003-01-01	65.0491596502394
2004-01-01	65.4524864536258
2005-01-01	65.8815624601918
2006-01-01	66.2411674204887
2007-01-01	66.6471464783931
2008-01-01	67.0636092157544
2009-01-01	67.4376804161495
2010-01-01	67.7447042284875
2011-01-01	68.0228969790232
2012-01-01	68.2339218209325
2013-01-01	68.3954121942596
2014-01-01	68.5377469003070
2015-01-01	68.6742252232110
2016-01-01	68.7790882692129
2017-01-01	68.8741881661934