Year	Percent of Total
1960-01-01	67.0760394275092
1961-01-01	66.6545476758699
1962-01-01	66.1368256866215
1963-01-01	65.5778318838826
1964-01-01	65.0588242554170
1965-01-01	64.6192520172137
1966-01-01	64.1132927231352
1967-01-01	63.7211386467863
1968-01-01	63.4264193613594
1969-01-01	63.2086006008131
1970-01-01	63.0686509245977
1971-01-01	62.9258007909161
1972-01-01	62.9266892793587
1973-01-01	63.0435175055692
1974-01-01	63.2359312707670
1975-01-01	63.4822811582175
1976-01-01	63.8406405949979
1977-01-01	64.1516945717672
1978-01-01	64.5075308014852
1979-01-01	65.0327893057673
1980-01-01	65.7671181529144
1981-01-01	66.3935756991031
1982-01-01	67.2468935984069
1983-01-01	68.1782111549442
1984-01-01	68.9641759502327
1985-01-01	69.4795547217715
1986-01-01	69.6965241689417
1987-01-01	69.6946512191559
1988-01-01	69.5266944641779
1989-01-01	69.3132404106378
1990-01-01	69.1313666065180
1991-01-01	68.8696437230626
1992-01-01	68.6547013118943
1993-01-01	68.4861099506001
1994-01-01	68.3548034430942
1995-01-01	68.2590321460436
1996-01-01	68.1851315502501
1997-01-01	68.1171119962332
1998-01-01	68.0483062711560
1999-01-01	67.9628073632122
2000-01-01	67.8446088533275
2001-01-01	67.6123684885205
2002-01-01	67.3802160734760
2003-01-01	67.1480567259006
2004-01-01	66.9247995662619
2005-01-01	66.7260751808893
2006-01-01	66.5178699925422
2007-01-01	66.3270356577584
2008-01-01	66.1555053519407
2009-01-01	66.0124251268551
2010-01-01	65.8950017606203
2011-01-01	65.8610721973638
2012-01-01	65.8692075817318
2013-01-01	65.8798344023014
2014-01-01	65.8508907755905
2015-01-01	65.7636764592908
2016-01-01	65.6409281599760
2017-01-01	65.4718322613631