Year	Percent
1968-01-01	87.0110588337280
1969-01-01	87.3513314442392
1970-01-01	86.7831779281634
1971-01-01	87.2646741564608
1972-01-01	86.5206745952091
1973-01-01	86.8266058497744
1974-01-01	86.5002553184124
1975-01-01	86.4958428390350
1976-01-01	86.4223765863019
1977-01-01	85.1244684889782
1978-01-01	85.3221374734210
1979-01-01	85.5697483734720
1980-01-01	85.6961728403542
1981-01-01	85.2705789566413
1982-01-01	85.1890974476518
1983-01-01	84.9900089388892
1984-01-01	84.1511628791529
1985-01-01	83.5054164179583
1986-01-01	83.2848948024358
1987-01-01	83.0090212039142
1988-01-01	82.5145082715001
1989-01-01	82.9373924603817
1990-01-01	83.6141415099155
1991-01-01	84.7304298365870
1992-01-01	85.0628234575819
1993-01-01	85.3410870255979
1994-01-01	85.1409516238352
1995-01-01	84.9271551116879
1996-01-01	85.1217298203026
1997-01-01	85.1592279832411
1998-01-01	85.1561250855066
1999-01-01	85.2408811076081
2000-01-01	84.1837758030237
2001-01-01	83.4219621875196
2002-01-01	82.9125399512744
2003-01-01	83.0714047316920
2004-01-01	82.7250447034380
2005-01-01	83.0797556282093
2006-01-01	83.8077068254088
2007-01-01	84.9351698827076
2008-01-01	85.1574727369752
2009-01-01	84.6289430706855
2010-01-01	84.1383196986462
2011-01-01	83.7851731548122
2012-01-01	82.9098944622737
2013-01-01	83.5902332240954
2014-01-01	84.8778196098399
2015-01-01	85.7081838117433
2016-01-01	86.5407125895514
2017-01-01	87.6626964890896