Year	Percent
1979-01-01	50.5542
1980-01-01	52.5644
1981-01-01	58.9738
1982-01-01	63.2316
1983-01-01	62.0085
1984-01-01	59.2714
1985-01-01	54.0141
1986-01-01	48.7104
1987-01-01	53.9965
1988-01-01	64.7302
1989-01-01	69.3252
1990-01-01	69.0401
1991-01-01	68.5537
1992-01-01	73.2507
1993-01-01	76.5926
1994-01-01	78.9382
1995-01-01	76.2278
1996-01-01	72.7443
1997-01-01	72.8772
1998-01-01	71.6377
1999-01-01	71.2517
2000-01-01	67.5933
2001-01-01	62.0746
2002-01-01	57.8776
2003-01-01	54.4442
2004-01-01	51.2094
2005-01-01	49.5778
2006-01-01	49.1291
2007-01-01	48.9391
2008-01-01	52.6389
2009-01-01	56.7041
2010-01-01	56.4348
2011-01-01	54.1753
2012-01-01	49.6805
2013-01-01	44.4173
2014-01-01	40.6206
2015-01-01	39.0304
2016-01-01	39.0439