Year	Percent
1978-01-01	50.4822822196964
1979-01-01	50.0912796570442
1980-01-01	49.9659250881506
1981-01-01	49.9003587797465
1982-01-01	49.3993259795059
1983-01-01	48.2119649601765
1984-01-01	48.1471671630385
1985-01-01	48.1269097627487
1986-01-01	48.0883179848624
1987-01-01	47.9368095866277
1988-01-01	47.6090947012275
1989-01-01	46.8232240590992
1990-01-01	46.0685896544681
1991-01-01	45.3789498501847
1992-01-01	45.3391462229320
1993-01-01	45.7487089768542
1994-01-01	45.8418600084294
1995-01-01	45.9065371696272
1996-01-01	45.6759930118691
1997-01-01	45.0902910394537
1998-01-01	45.1563438849017
1999-01-01	45.4782559530283
2000-01-01	45.6238146452382
2001-01-01	45.5077265850299
2002-01-01	45.9373668485230
2003-01-01	45.9098272058061
2004-01-01	45.7084343573977
2005-01-01	45.2614445123306
2006-01-01	44.8917000379871
2007-01-01	44.5662893789995
2008-01-01	44.3488278273523
2009-01-01	43.8799347349238
2010-01-01	43.6145925429613
2011-01-01	43.6862462588691
2012-01-01	43.4621653364359
2013-01-01	42.2854230811570
2014-01-01	41.6092795094195
2015-01-01	40.9815720418790
2016-01-01	39.8069291978302
2017-01-01	38.5573712187231