Year Percent 1960-01-01 2.88365000000000000 1961-01-01 2.21457000000000000 1962-01-01 1.54757000000000010 1963-01-01 1.37295000000000000 1964-01-01 1.66218000000000000 1965-01-01 1.46884000000000000 1966-01-01 1.24140000000000000 1967-01-01 0.42614900000000000 1968-01-01 0.42614900000000000 1969-01-01 0.42614900000000000 1970-01-01 0.04775600000000000 1971-01-01 0.04775600000000000 1972-01-01 0.04775600000000000 1973-01-01 0.04775600000000000 1974-01-01 1.56664000000000000 1975-01-01 3.68574000000000000 1976-01-01 2.52445000000000000 1977-01-01 1.53387000000000000 1978-01-01 2.06665999999999970 1979-01-01 4.56935000000000000 1980-01-01 7.60483000000000100 1981-01-01 8.89126000000000000 1982-01-01 7.33186999999999900 1983-01-01 6.58806000000000050 1984-01-01 6.28671000000000000 1985-01-01 7.05296999999999900 1986-01-01 6.47365000000000000 1987-01-01 5.72889000000000000 1988-01-01 7.09331999999999900 1989-01-01 5.74465000000000000 1990-01-01 5.39603000000000050 1991-01-01 7.85872000000000000 1992-01-01 10.44130000000000000 1993-01-01 12.49010000000000000 1994-01-01 10.99220000000000000 1995-01-01 11.01530000000000000 1996-01-01 12.54870000000000000 1997-01-01 11.50670000000000000 1998-01-01 10.85900000000000200 1999-01-01 9.86358000000000000 2000-01-01 10.47760000000000000 2001-01-01 10.86350000000000000 2002-01-01 7.29566000000000100 2003-01-01 7.98760000000000000 2004-01-01 7.39737000000000000 2005-01-01 9.51763000000000000 2006-01-01 11.10140000000000000 2007-01-01 9.82417000000000000 2008-01-01 4.64524000000000000 2009-01-01 0.11652100000000000 2010-01-01 0.11844300000000000 2011-01-01 0.11906600000000000 2012-01-01 0.12031700000000001 2013-01-01 0.12395899999999999 2014-01-01 0.11994000000000000 2015-01-01 0.11528300000000000 2016-01-01 0.10849400000000001