Year	Percent
1973-01-01	26.071200000000000
1974-01-01	28.777100000000000
1975-01-01	30.043600000000000
1976-01-01	30.446800000000000
1977-01-01	35.436600000000000
1978-01-01	38.138400000000000
1979-01-01	40.789500000000000
1980-01-01	40.977200000000000
1981-01-01	41.689200000000000
1982-01-01	41.985100000000000
1983-01-01	42.523900000000000
1984-01-01	37.747800000000000
1985-01-01	35.123100000000000
1986-01-01	35.751900000000000
1987-01-01	39.306600000000000
1988-01-01	41.627800000000000
1989-01-01	39.095500000000000
1990-01-01	39.127400000000000
1991-01-01	38.545700000000000
1992-01-01	39.559400000000000
1993-01-01	36.456100000000000
1994-01-01	26.731100000000000
1995-01-01	23.677200000000000
1996-01-01	22.714400000000000
1997-01-01	22.140300000000000
1998-01-01	21.784600000000000
1999-01-01	20.415400000000000
2000-01-01	19.462000000000000
2001-01-01	18.789300000000000
2002-01-01	18.205200000000000
2003-01-01	16.969300000000000
2004-01-01	16.999300000000000
2005-01-01	17.129200000000000
2006-01-01	17.577500000000000
2007-01-01	19.242900000000000
2008-01-01	19.179700000000000
2009-01-01	18.905000000000000
2010-01-01	20.040200000000000
2011-01-01	22.828000000000003
2012-01-01	21.567500000000000
2013-01-01	22.611300000000000
2014-01-01	24.681900000000000
2015-01-01	28.108100000000000
2016-01-01	30.563600000000000