Year	Percent
1960-01-01	83.6646114701512
1961-01-01	83.8437414713236
1962-01-01	83.3254726633528
1963-01-01	82.1390194111665
1964-01-01	81.2802694006774
1965-01-01	80.8101376885113
1966-01-01	80.7270047333006
1967-01-01	80.7438977903863
1968-01-01	81.2243381786467
1969-01-01	81.0412076252058
1970-01-01	80.9217579199049
1971-01-01	81.2555122291402
1972-01-01	80.9960739147699
1973-01-01	81.2014309194773
1974-01-01	80.8457165631720
1975-01-01	79.9567597081883
1976-01-01	79.5609339668271
1977-01-01	79.0590609461371
1978-01-01	78.6898610634538
1979-01-01	78.7062358906880
1980-01-01	78.5032295842159
1981-01-01	78.3217936448001
1982-01-01	77.9384813226332
1983-01-01	77.6997812442018
1984-01-01	77.1296730700429
1985-01-01	76.5842928435396
1986-01-01	76.1175559877652
1987-01-01	75.5867718821680
1988-01-01	75.6047955398630
1989-01-01	75.6827064988835
1990-01-01	76.0085013759706
1991-01-01	76.4095911786098
1992-01-01	76.5097587218851
1993-01-01	76.2585010852534
1994-01-01	75.6665436869504
1995-01-01	75.2861269497843
1996-01-01	75.1872486840271
1997-01-01	75.2197983389160
1998-01-01	74.1467967404808
1999-01-01	73.3338412250542
2000-01-01	72.7623485564361
2001-01-01	71.8005461503931
2002-01-01	70.6433113727580
2003-01-01	70.1290532359128
2004-01-01	69.9050903127338
2005-01-01	70.0168237230592
2006-01-01	70.0967497900741
2007-01-01	70.3483486077218
2008-01-01	69.8995355708987
2009-01-01	68.3490030119667
2010-01-01	67.9309293612232
2011-01-01	67.8517871137372
2012-01-01	67.5677127608127
2013-01-01	67.5581623773092
2014-01-01	67.8287131030440
2015-01-01	67.8733435629902
2016-01-01	68.1552938321010
2017-01-01	68.4693430312779