Year	Percent of Total
1960-01-01	53.1722190884615
1961-01-01	52.7731931707735
1962-01-01	52.4233470602155
1963-01-01	52.1340574021934
1964-01-01	51.9277139569543
1965-01-01	51.8126689121924
1966-01-01	51.5823877290495
1967-01-01	51.4733877800348
1968-01-01	51.4497269259600
1969-01-01	51.4742547300694
1970-01-01	51.5317376683452
1971-01-01	51.4622154358003
1972-01-01	51.4623258602434
1973-01-01	51.5145335417238
1974-01-01	51.5985590909502
1975-01-01	51.6969007641386
1976-01-01	51.7547906633717
1977-01-01	51.8332585174748
1978-01-01	51.9299543294888
1979-01-01	52.0519813870585
1980-01-01	52.2040420306683
1981-01-01	52.2908689436162
1982-01-01	52.4186797939311
1983-01-01	52.5754930912185
1984-01-01	52.7462322042986
1985-01-01	52.9239732547931
1986-01-01	52.9953617282253
1987-01-01	53.0980240711264
1988-01-01	53.2255390862883
1989-01-01	53.3857788470568
1990-01-01	53.5540192138226
1991-01-01	53.7727362048441
1992-01-01	53.9540842256441
1993-01-01	54.2967321623225
1994-01-01	54.6931708415314
1995-01-01	55.2155389612456
1996-01-01	55.6538629623031
1997-01-01	56.1204172897831
1998-01-01	56.6048803447516
1999-01-01	57.1004340596587
2000-01-01	57.6054769222472
2001-01-01	58.1409735334042
2002-01-01	58.6765039840381
2003-01-01	59.2066688583407
2004-01-01	59.7254796280358
2005-01-01	60.2244918696922
2006-01-01	60.6984166983216
2007-01-01	61.1621916094245
2008-01-01	61.5865394622257
2009-01-01	61.9395425237997
2010-01-01	62.2064786002635
2011-01-01	62.3426195882843
2012-01-01	62.4020274349147
2013-01-01	62.4087154200516
2014-01-01	62.4047567314246
2015-01-01	62.4182168455797
2016-01-01	62.3851440372785
2017-01-01	62.4231161621907