Year	Percent
1960-01-01	50.0765479134906
1961-01-01	48.9693564787956
1962-01-01	49.4819646124287
1963-01-01	48.4513713257026
1964-01-01	48.9592129667717
1965-01-01	50.1719303381642
1966-01-01	52.1538031042604
1967-01-01	52.7005630394908
1968-01-01	52.7008229594730
1969-01-01	53.9901545249330
1970-01-01	53.1881982256730
1971-01-01	52.2924013659584
1972-01-01	54.3270315374250
1973-01-01	56.9707495889725
1974-01-01	57.2011952371416
1975-01-01	54.2221362701133
1976-01-01	55.7178638380142
1977-01-01	57.5720146187218
1978-01-01	59.8178883533117
1979-01-01	60.5496297482970
1980-01-01	58.6271348192310
1981-01-01	57.6432029849440
1982-01-01	55.2870959642414
1983-01-01	55.6290117664478
1984-01-01	58.3094724821185
1985-01-01	59.0014966185817
1986-01-01	59.4877350960125
1987-01-01	60.0571227085708
1988-01-01	60.8295901091740
1989-01-01	61.1171500176487
1990-01-01	59.7877805926663
1991-01-01	57.1559431172209
1992-01-01	56.7235357788949
1993-01-01	57.2321253760258
1994-01-01	58.1264560503664
1995-01-01	58.2595344892391
1996-01-01	57.6248294361068
1997-01-01	58.0373281333742
1998-01-01	58.9895251176711
1999-01-01	58.9943217281610
2000-01-01	59.6593652453439
2001-01-01	57.7164582726859
2002-01-01	55.6931957915101
2003-01-01	53.9061522037016
2004-01-01	53.8989417953746
2005-01-01	53.9049667740546
2006-01-01	54.2449504864837
2007-01-01	53.1272488372784
2008-01-01	51.2260985659641
2009-01-01	46.8519857297959
2010-01-01	45.0023061028042
2011-01-01	45.4538807633328
2012-01-01	45.9837950171171
2013-01-01	46.4916718712544
2014-01-01	47.6392167636933
2015-01-01	48.6050373066938
2016-01-01	49.4130027394952
2017-01-01	50.3426217117978