Year	Percent
1963-01-01	13.028400000000000
1964-01-01	12.126400000000000
1965-01-01	13.374000000000000
1966-01-01	14.523200000000000
1967-01-01	14.826300000000000
1968-01-01	14.996400000000000
1969-01-01	16.050600000000000
1970-01-01	17.397100000000000
1971-01-01	15.886500000000000
1972-01-01	15.010200000000000
1973-01-01	14.271200000000000
1974-01-01	13.892100000000000
1975-01-01	13.827500000000000
1976-01-01	14.103200000000000
1977-01-01	14.316600000000000
1978-01-01	13.658600000000000
1979-01-01	13.200200000000000
1980-01-01	21.753600000000000
1981-01-01	18.937900000000000
1982-01-01	19.122900000000000
1983-01-01	18.841700000000000
1984-01-01	17.856800000000000
1985-01-01	14.758700000000000
1986-01-01	15.550400000000000
1987-01-01	16.564200000000000
1988-01-01	15.481400000000000
1989-01-01	15.371400000000000
1990-01-01	15.957300000000000
1991-01-01	15.386000000000000
1992-01-01	15.418000000000000
1993-01-01	16.582500000000000
1994-01-01	19.345200000000000
1995-01-01	21.460000000000000
1996-01-01	24.070500000000000
1997-01-01	21.450300000000000
1998-01-01	17.544200000000000
1999-01-01	16.442700000000000
2000-01-01	18.040200000000000
2001-01-01	17.098200000000000
2002-01-01	15.800000000000000
2003-01-01	15.602900000000000
2004-01-01	15.357800000000000
2005-01-01	16.879500000000000
2006-01-01	16.826200000000000
2007-01-01	14.795400000000000
2008-01-01	14.664700000000000
2009-01-01	15.640999999999998
2010-01-01	17.099600000000000
2011-01-01	18.238200000000000
2012-01-01	18.224700000000000
2013-01-01	26.659200000000000
2014-01-01	27.775800000000000
2015-01-01	27.548500000000000