Year	Percent
1968-01-01	64.9515673946269
1969-01-01	64.8551768924318
1970-01-01	64.2116435265201
1971-01-01	64.5428426545696
1972-01-01	63.2659438176519
1973-01-01	63.8231732561673
1974-01-01	63.1048777038100
1975-01-01	62.8170651180050
1976-01-01	62.9158717448405
1977-01-01	62.4204292540461
1978-01-01	62.9634245062456
1979-01-01	63.1806343456518
1980-01-01	63.3007591970184
1981-01-01	62.9160261385929
1982-01-01	63.2050155156221
1983-01-01	63.9010731099482
1984-01-01	63.1055339913177
1985-01-01	63.1894598375062
1986-01-01	62.9557043345784
1987-01-01	63.2073893118824
1988-01-01	63.2232604229476
1989-01-01	63.9443182548965
1990-01-01	64.9301027207959
1991-01-01	66.2111403681333
1992-01-01	66.3644832255858
1993-01-01	66.5376295099672
1994-01-01	66.1378591681087
1995-01-01	66.2537232801069
1996-01-01	66.4337252190311
1997-01-01	66.8827525268260
1998-01-01	67.0907354286730
1999-01-01	67.1705866479914
2000-01-01	66.4922976711929
2001-01-01	65.8040158867040
2002-01-01	65.5305024425686
2003-01-01	65.8995168602740
2004-01-01	66.0915655423604
2005-01-01	66.6042036747826
2006-01-01	67.3498965939136
2007-01-01	68.5020631338573
2008-01-01	68.9678086584448
2009-01-01	68.9399630251482
2010-01-01	68.9143704592754
2011-01-01	68.9616288270634
2012-01-01	68.2983135562789
2013-01-01	69.5510808702766
2014-01-01	71.0412108514732
2015-01-01	72.4069045905854
2016-01-01	73.6958863315008
2017-01-01	75.4183318274783