Year	Percent
1971-01-01	57.750800000000000
1972-01-01	64.414400000000000
1973-01-01	80.628800000000000
1974-01-01	91.718600000000000
1975-01-01	82.979400000000000
1976-01-01	76.340400000000000
1977-01-01	87.105500000000000
1978-01-01	96.754300000000000
1979-01-01	93.089900000000000
1980-01-01	77.564300000000000
1981-01-01	67.339500000000000
1982-01-01	66.710000000000000
1983-01-01	63.030300000000000
1984-01-01	52.248500000000000
1985-01-01	40.058100000000000
1986-01-01	29.847800000000000
1987-01-01	24.546700000000000
1988-01-01	21.633300000000000
1989-01-01	21.404900000000000
1990-01-01	21.610700000000000
1991-01-01	20.735200000000000
1992-01-01	19.646700000000000
1993-01-01	17.659200000000000
1994-01-01	16.884600000000000
1995-01-01	17.504400000000000
1996-01-01	17.861400000000000
1997-01-01	18.426300000000000
1998-01-01	19.108700000000000
1999-01-01	18.491500000000000
2000-01-01	18.710100000000000
2001-01-01	20.019000000000002
2002-01-01	20.956999999999997
2003-01-01	23.771500000000000
2004-01-01	27.879800000000000
2005-01-01	30.245100000000000
2006-01-01	30.374000000000002
2007-01-01	35.197300000000000
2008-01-01	45.251300000000000
2009-01-01	44.293900000000000
2010-01-01	41.095000000000000
2011-01-01	42.423200000000000
2012-01-01	43.905400000000000
2013-01-01	42.501800000000000
2014-01-01	39.513900000000000
2015-01-01	40.316900000000000
2016-01-01	40.924900000000000