Year	Percent
1975-01-01	37.0498
1976-01-01	35.9909
1977-01-01	34.7536
1978-01-01	29.9326
1979-01-01	33.7310
1980-01-01	32.0448
1981-01-01	35.8542
1982-01-01	36.6935
1983-01-01	36.1210
1984-01-01	34.6573
1985-01-01	33.3569
1986-01-01	30.6082
1987-01-01	26.7119
1988-01-01	26.6142
1989-01-01	33.1520
1990-01-01	39.8502
1991-01-01	46.1691
1992-01-01	49.8921
1993-01-01	52.4043
1994-01-01	53.9599
1995-01-01	57.8648
1996-01-01	57.4412
1997-01-01	58.2156
1998-01-01	57.8756
1999-01-01	58.8966
2000-01-01	62.3157
2001-01-01	63.2439
2002-01-01	62.9417
2003-01-01	58.8960
2004-01-01	53.8109
2005-01-01	55.8847
2006-01-01	56.5172
2007-01-01	55.2301
2008-01-01	55.1344
2009-01-01	53.7372
2010-01-01	57.9443
2011-01-01	61.0409
2012-01-01	66.3901
2013-01-01	66.7638
2014-01-01	64.5098
2015-01-01	61.5975
2016-01-01	55.6953