Year	Percent of Total
1960-01-01	52.6304586062346
1961-01-01	52.1859516700808
1962-01-01	51.7978476243157
1963-01-01	51.4789072668232
1964-01-01	51.2278975039721
1965-01-01	51.0302860880796
1966-01-01	50.7403205375337
1967-01-01	50.4882034958607
1968-01-01	50.2832651041490
1969-01-01	50.1345008418474
1970-01-01	50.0577851512750
1971-01-01	50.4567059744874
1972-01-01	50.8347401453000
1973-01-01	51.2244791520884
1974-01-01	51.6706565000195
1975-01-01	52.1891871430299
1976-01-01	52.9191922962659
1977-01-01	53.6760875422028
1978-01-01	54.4033150684514
1979-01-01	55.0220707682741
1980-01-01	55.5084629181266
1981-01-01	56.0701187271259
1982-01-01	56.4842108812815
1983-01-01	56.8069802603722
1984-01-01	57.1474484333106
1985-01-01	57.5710466736725
1986-01-01	57.8439077295870
1987-01-01	58.2390492764227
1988-01-01	58.6692865149501
1989-01-01	59.0087652759214
1990-01-01	59.2092122749564
1991-01-01	59.5407888997439
1992-01-01	59.7467304198616
1993-01-01	59.8923421046647
1994-01-01	60.0843288711687
1995-01-01	60.3702670262754
1996-01-01	60.6888403180844
1997-01-01	61.0562329458772
1998-01-01	61.4371171319327
1999-01-01	61.7805818502765
2000-01-01	62.0756834741844
2001-01-01	62.4740387609424
2002-01-01	62.8628160226158
2003-01-01	63.2455027005696
2004-01-01	63.6277715309571
2005-01-01	64.0098429944237
2006-01-01	64.4474407195886
2007-01-01	64.8633501760942
2008-01-01	65.2735518000020
2009-01-01	65.6817778106348
2010-01-01	66.0748372262564
2011-01-01	66.4088356505396
2012-01-01	66.7505864455743
2013-01-01	67.0783071671691
2014-01-01	67.3541200444219
2015-01-01	67.5537033002340
2016-01-01	67.6774330247623
2017-01-01	67.7028057487997