Year	Percent
1968-01-01	58.3171247663390
1969-01-01	57.2135126068402
1970-01-01	57.6876456330991
1971-01-01	59.1817164552283
1972-01-01	57.8320074195181
1973-01-01	55.4672967625140
1974-01-01	53.0235564655904
1975-01-01	50.2408782512924
1976-01-01	48.3707770576392
1977-01-01	45.9679001104097
1978-01-01	44.9906399190687
1979-01-01	43.9006040784947
1980-01-01	42.9892697488315
1981-01-01	43.4305838405435
1982-01-01	43.3933120848483
1983-01-01	44.0860081709800
1984-01-01	43.4298390527210
1985-01-01	42.6696751021022
1986-01-01	42.8005282244537
1987-01-01	42.4090173011118
1988-01-01	42.2278551928341
1989-01-01	42.5347442009357
1990-01-01	43.6659856457369
1991-01-01	45.3397021936960
1992-01-01	46.7892427054617
1993-01-01	47.6640610645876
1994-01-01	48.1232254682062
1995-01-01	48.0866659925943
1996-01-01	49.0187592803199
1997-01-01	49.4710438730648
1998-01-01	48.9234240101501
1999-01-01	47.8379652796220
2000-01-01	47.4340053011400
2001-01-01	46.6034744403070
2002-01-01	46.0807088348682
2003-01-01	45.2777335917872
2004-01-01	44.2215826151777
2005-01-01	44.4721186436593
2006-01-01	44.6470227178730
2007-01-01	44.9936508560509
2008-01-01	44.3148079765462
2009-01-01	42.5667070169130
2010-01-01	41.9961000434852
2011-01-01	41.9903547276273
2012-01-01	41.4941646966448
2013-01-01	41.6850391642648
2014-01-01	42.1704570585947
2015-01-01	42.4081341339002
2016-01-01	44.3599658966411
2017-01-01	44.2555473651688