Year	Percent
1968-01-01	44.1349954959133
1969-01-01	44.9332109000466
1970-01-01	44.3777597289014
1971-01-01	43.9149701333566
1972-01-01	45.6734162386674
1973-01-01	47.1835151454209
1974-01-01	49.9229133312814
1975-01-01	52.0126691209426
1976-01-01	53.6160810478952
1977-01-01	54.6308997020862
1978-01-01	55.1773085914230
1979-01-01	55.8699627317399
1980-01-01	56.5379531672004
1981-01-01	56.3235744810642
1982-01-01	56.5281978519641
1983-01-01	55.7147918957445
1984-01-01	56.1171848740454
1985-01-01	56.9579864153606
1986-01-01	56.6988323889037
1987-01-01	57.1841447772045
1988-01-01	57.2330122805409
1989-01-01	56.6593260097210
1990-01-01	55.7186861990429
1991-01-01	54.3847524210223
1992-01-01	53.3326945151383
1993-01-01	52.8101871721873
1994-01-01	52.3058745129270
1995-01-01	52.2971303454626
1996-01-01	51.6656278855156
1997-01-01	51.4071450531930
1998-01-01	51.6475424969496
1999-01-01	52.6222494082345
2000-01-01	52.8815195918439
2001-01-01	53.4769580575885
2002-01-01	54.4698287121260
2003-01-01	55.0841767048232
2004-01-01	55.6904840533708
2005-01-01	55.2290445896113
2006-01-01	55.0702402682799
2007-01-01	55.1285878138360
2008-01-01	55.5458969333031
2009-01-01	56.4818556860913
2010-01-01	57.2160726483939
2011-01-01	57.3938403509473
2012-01-01	58.2632669300714
2013-01-01	57.5779174979854
2014-01-01	57.2727229609391
2015-01-01	57.3069258124203
2016-01-01	55.5396441443843
2017-01-01	55.3678000304244