Year	Percent
1960-01-01	17.709200000000000
1961-01-01	16.727400000000000
1962-01-01	15.806500000000000
1963-01-01	41.292100000000000
1964-01-01	57.675200000000000
1965-01-01	62.093700000000000
1966-01-01	63.014200000000000
1967-01-01	62.647800000000000
1968-01-01	63.187900000000000
1969-01-01	66.138800000000000
1970-01-01	70.545400000000000
1971-01-01	73.139800000000000
1972-01-01	72.937200000000000
1973-01-01	75.154700000000000
1974-01-01	80.135700000000000
1975-01-01	72.953500000000000
1976-01-01	56.786100000000000
1977-01-01	51.320800000000000
1978-01-01	52.509800000000000
1979-01-01	52.707600000000000
1980-01-01	50.736400000000000
1981-01-01	51.818000000000005
1982-01-01	53.310300000000000
1983-01-01	53.223000000000000
1984-01-01	51.537400000000000
1985-01-01	52.940000000000000
1986-01-01	55.186900000000000
1987-01-01	55.013000000000005
1988-01-01	54.188900000000000
1989-01-01	51.804900000000000
1990-01-01	51.507600000000000
1991-01-01	48.207900000000000
1992-01-01	43.096700000000000
1993-01-01	40.594100000000000
1994-01-01	41.150600000000000
1995-01-01	46.281900000000000
1996-01-01	54.546400000000000
1997-01-01	58.410800000000000
1998-01-01	58.351200000000000
1999-01-01	60.656200000000000
2000-01-01	59.347300000000000
2001-01-01	59.479000000000000
2002-01-01	60.664300000000000
2003-01-01	60.264900000000000
2004-01-01	55.659700000000000
2005-01-01	51.412900000000000
2006-01-01	56.044000000000000
2007-01-01	60.758000000000000
2008-01-01	59.946600000000000