Year	Percent of Total
1960-01-01	52.1919384890647
1961-01-01	51.9542526177109
1962-01-01	51.7920083824140
1963-01-01	51.6574827837934
1964-01-01	51.4756336822342
1965-01-01	51.1941495032195
1966-01-01	50.8531323125345
1967-01-01	50.6723582813356
1968-01-01	50.5897648615873
1969-01-01	50.5973278886532
1970-01-01	50.7275819078685
1971-01-01	50.3345224883137
1972-01-01	49.9936742975547
1973-01-01	49.7399294622913
1974-01-01	49.6137583529401
1975-01-01	49.6221856612817
1976-01-01	48.7680825482567
1977-01-01	48.2592302407709
1978-01-01	48.0097503170598
1979-01-01	47.8943145819699
1980-01-01	47.8317670574144
1981-01-01	48.1666411370421
1982-01-01	48.4153723183569
1983-01-01	48.6532557067184
1984-01-01	48.9623899629841
1985-01-01	49.3433840299587
1986-01-01	49.6004051406369
1987-01-01	49.9774770238469
1988-01-01	50.3888802805816
1989-01-01	50.7453410477632
1990-01-01	51.0377797786991
1991-01-01	52.2792867223153
1992-01-01	53.3592073782609
1993-01-01	54.3582171421370
1994-01-01	55.3668339948130
1995-01-01	56.4076131928420
1996-01-01	56.5195331242885
1997-01-01	56.7100286470098
1998-01-01	56.9546290599345
1999-01-01	57.2147116023673
2000-01-01	57.4782143508004
2001-01-01	57.7320957307641
2002-01-01	58.0354224917390
2003-01-01	58.3602166775930
2004-01-01	58.6528096798989
2005-01-01	58.8536519504084
2006-01-01	59.0175274576390
2007-01-01	59.1356701254652
2008-01-01	59.2109922275218
2009-01-01	59.2707263738074
2010-01-01	59.3312532457859
2011-01-01	59.4273910707975
2012-01-01	59.5602942882098
2013-01-01	59.7244488120470
2014-01-01	59.9317698806240
2015-01-01	60.2096207767797
2016-01-01	60.4335941044451
2017-01-01	60.6851245259784