Year	Percent of Total
1960-01-01	55.5408261975565
1961-01-01	55.3796555972008
1962-01-01	55.4353105587416
1963-01-01	55.5918730116539
1964-01-01	55.6975639340948
1965-01-01	55.6825326961771
1966-01-01	55.4899254129742
1967-01-01	55.2527141178470
1968-01-01	54.9963329338318
1969-01-01	54.7878271589548
1970-01-01	54.6649189912203
1971-01-01	54.3455184659782
1972-01-01	54.1495700293984
1973-01-01	54.0406686322766
1974-01-01	53.9834131402625
1975-01-01	53.9567749198530
1976-01-01	53.7505360279980
1977-01-01	53.6228584286036
1978-01-01	53.5637182654184
1979-01-01	53.5730642441934
1980-01-01	53.6520094239097
1981-01-01	53.4271373519197
1982-01-01	53.3160886208096
1983-01-01	53.2865448899732
1984-01-01	53.2894736842105
1985-01-01	53.2899665652064
1986-01-01	53.2156404777286
1987-01-01	53.1287654589888
1988-01-01	53.0702356395946
1989-01-01	53.1232968164494
1990-01-01	53.3522558070280
1991-01-01	53.0144206788216
1992-01-01	52.8072997507173
1993-01-01	52.6906982567953
1994-01-01	52.5662000027105
1995-01-01	52.3610493379972
1996-01-01	52.8102264280295
1997-01-01	53.2710863653041
1998-01-01	53.7682028202267
1999-01-01	54.3735640121031
2000-01-01	55.1224590872944
2001-01-01	56.2969810040705
2002-01-01	57.5721595846959
2003-01-01	58.8719896572853
2004-01-01	60.1177293754939
2005-01-01	61.2753735309660
2006-01-01	62.1797961405951
2007-01-01	63.0179719866425
2008-01-01	63.7929952207718
2009-01-01	64.5328346802751
2010-01-01	65.2547066479212
2011-01-01	65.8022173907172
2012-01-01	66.3771453463432
2013-01-01	66.9439357039117
2014-01-01	67.4589927464557
2015-01-01	67.9026551145182
2016-01-01	68.2766228149894
2017-01-01	68.5653966642315