Year	Percent of Total
1960-01-01	55.0843611278545
1961-01-01	53.9809494035213
1962-01-01	52.8749767765212
1963-01-01	51.8817750018076
1964-01-01	51.1349793535066
1965-01-01	50.6941151110153
1966-01-01	50.2216127204664
1967-01-01	50.1211634498862
1968-01-01	50.2930203911710
1969-01-01	50.6033206294251
1970-01-01	50.9930550528231
1971-01-01	51.5661178700403
1972-01-01	52.1732905722223
1973-01-01	52.8647564035131
1974-01-01	53.7072888579957
1975-01-01	54.7070153575777
1976-01-01	55.6779800871042
1977-01-01	56.7599000807418
1978-01-01	57.8995990049563
1979-01-01	59.0093406534410
1980-01-01	60.0289916429541
1981-01-01	60.8534368539297
1982-01-01	61.5599700010615
1983-01-01	62.1356599023322
1984-01-01	62.5779002483384
1985-01-01	62.8862416381720
1986-01-01	62.8645775630574
1987-01-01	62.7533328497860
1988-01-01	62.5865830075623
1989-01-01	62.3845797557448
1990-01-01	62.1561502022016
1991-01-01	61.7854061644294
1992-01-01	61.4773446175173
1993-01-01	61.2412076824896
1994-01-01	61.0977328787438
1995-01-01	61.0737469561153
1996-01-01	61.2117186403045
1997-01-01	61.4841725032928
1998-01-01	61.8877898908422
1999-01-01	62.4017506557199
2000-01-01	63.0023781381187
2001-01-01	63.7613530050643
2002-01-01	64.5144535801856
2003-01-01	65.3081634217595
2004-01-01	66.1967465044488
2005-01-01	67.1846552001580
2006-01-01	68.0381034264000
2007-01-01	68.9703843424072
2008-01-01	69.8920346936286
2009-01-01	70.6799230469879
2010-01-01	71.2664117858518
2011-01-01	71.5699841434517
2012-01-01	71.6839233422167
2013-01-01	71.6356857479037
2014-01-01	71.5059843087549
2015-01-01	71.3514054195463
2016-01-01	70.9815846708652
2017-01-01	70.7047679751361