Year	Percent
1968-01-01	55.8650045040867
1969-01-01	55.0667890999534
1970-01-01	55.6222402710986
1971-01-01	56.0850298666434
1972-01-01	54.3265837613326
1973-01-01	52.8164848545791
1974-01-01	50.0770866687186
1975-01-01	47.9873308790574
1976-01-01	46.3839189521048
1977-01-01	45.3691002979138
1978-01-01	44.8226914085770
1979-01-01	44.1300372682601
1980-01-01	43.4620468327995
1981-01-01	43.6764255189358
1982-01-01	43.4718021480359
1983-01-01	44.2852081042555
1984-01-01	43.8828151259546
1985-01-01	43.0420135846394
1986-01-01	43.3011676110963
1987-01-01	42.8158552227955
1988-01-01	42.7669877194591
1989-01-01	43.3406739902790
1990-01-01	44.2813138009571
1991-01-01	45.6152475789777
1992-01-01	46.6673054848617
1993-01-01	47.1898128278127
1994-01-01	47.6941254870730
1995-01-01	47.7028696545374
1996-01-01	48.3343721144844
1997-01-01	48.5928549468070
1998-01-01	48.3524575030504
1999-01-01	47.3777505917655
2000-01-01	47.1184804081561
2001-01-01	46.5230419424115
2002-01-01	45.5301712878740
2003-01-01	44.9158232951768
2004-01-01	44.3095159466292
2005-01-01	44.7709554103887
2006-01-01	44.9297597317201
2007-01-01	44.8714121861640
2008-01-01	44.4541030666969
2009-01-01	43.5181443139087
2010-01-01	42.7839273516061
2011-01-01	42.6061596490527
2012-01-01	41.7367330699286
2013-01-01	42.4220825020146
2014-01-01	42.7272770390609
2015-01-01	42.6930741875797
2016-01-01	44.4603558556157
2017-01-01	44.6321999695756