Year	Percent
1973-01-01	15.757500000000000
1974-01-01	14.437800000000000
1975-01-01	14.816900000000000
1976-01-01	14.771400000000000
1977-01-01	14.233300000000000
1978-01-01	15.631900000000000
1979-01-01	15.973400000000000
1980-01-01	16.592500000000000
1981-01-01	18.316300000000000
1982-01-01	19.601600000000000
1983-01-01	20.830300000000000
1984-01-01	21.078400000000000
1985-01-01	20.343100000000000
1986-01-01	17.738200000000000
1987-01-01	17.892800000000000
1988-01-01	17.475600000000000
1989-01-01	16.283800000000000
1990-01-01	14.162400000000000
1991-01-01	14.817700000000000
1992-01-01	17.364500000000000
1993-01-01	17.317400000000000
1994-01-01	18.330100000000000
1995-01-01	20.420900000000000
1996-01-01	21.848000000000003
1997-01-01	22.145700000000000
1998-01-01	22.811999999999998
1999-01-01	23.809600000000000
2000-01-01	23.879900000000000
2001-01-01	24.018500000000000
2002-01-01	23.668400000000000
2003-01-01	26.141500000000000
2004-01-01	29.230800000000000
2005-01-01	31.461300000000000
2006-01-01	34.996300000000000
2007-01-01	36.656400000000000
2008-01-01	36.671500000000000
2009-01-01	36.150300000000000
2010-01-01	35.352500000000000
2011-01-01	34.597800000000000
2012-01-01	36.206700000000000
2013-01-01	38.114000000000004
2014-01-01	39.130600000000000
2015-01-01	39.922800000000000
2016-01-01	41.098200000000000