Year	Percent
1968-01-01	83.8479872578430
1969-01-01	83.7513131757989
1970-01-01	83.8350504873377
1971-01-01	84.3721502661287
1972-01-01	84.3082788406284
1973-01-01	84.6306417187202
1974-01-01	84.4336640001593
1975-01-01	83.6823822166859
1976-01-01	83.4794950613256
1977-01-01	83.0887926791577
1978-01-01	82.8890158361496
1979-01-01	83.0755793863219
1980-01-01	82.9406779839341
1981-01-01	82.8418711141451
1982-01-01	82.7187284901170
1983-01-01	82.5069181564991
1984-01-01	82.0758869523890
1985-01-01	81.5766571121426
1986-01-01	81.2046470096795
1987-01-01	80.7813832872218
1988-01-01	80.8538182459553
1989-01-01	81.0821959969780
1990-01-01	81.5207396899272
1991-01-01	82.0081297505361
1992-01-01	82.3801605697981
1993-01-01	82.3786070135536
1994-01-01	82.0013202854335
1995-01-01	81.8982681455673
1996-01-01	82.1798596211278
1997-01-01	82.5140891613581
1998-01-01	81.7472528586849
1999-01-01	81.1784406127266
2000-01-01	81.0696087530974
2001-01-01	80.5513231005863
2002-01-01	79.9509450440693
2003-01-01	79.9522157375914
2004-01-01	80.0917536750058
2005-01-01	80.5071152171868
2006-01-01	81.0828142510768
2007-01-01	81.8356479399838
2008-01-01	81.7150853249814
2009-01-01	80.3243051670534
2010-01-01	80.2083269996039
2011-01-01	80.5815663247644
2012-01-01	80.3729554770046
2013-01-01	80.8499657303014
2014-01-01	81.6433373124346
2015-01-01	81.9311866768845
2016-01-01	82.6031231805078
2017-01-01	83.0029094996570