Year Percent 1966-01-01 0.026900999999999998 1967-01-01 0.023555000000000000 1968-01-01 0.023555000000000000 1969-01-01 0.023555000000000000 1970-01-01 0.023555000000000000 1971-01-01 0.023555000000000000 1972-01-01 0.023555000000000000 1973-01-01 0.023555000000000000 1974-01-01 0.023555000000000000 1975-01-01 6.592980000000001000 1976-01-01 6.242100000000000000 1977-01-01 7.729719999999999500 1978-01-01 6.824540000000000000 1979-01-01 5.790669999999999500 1980-01-01 8.021920000000000000 1981-01-01 9.751700000000000000 1982-01-01 10.084400000000000000 1983-01-01 10.699600000000000000 1984-01-01 9.941430000000000000 1985-01-01 9.785900000000000000 1986-01-01 9.658160000000000000 1987-01-01 12.711400000000000000 1988-01-01 20.702200000000000000 1989-01-01 30.094900000000000000 1990-01-01 27.186700000000000000 1991-01-01 24.474200000000000000 1992-01-01 18.785600000000000000 1993-01-01 17.937700000000000000 1994-01-01 17.139800000000000000 1995-01-01 15.290600000000000000 1996-01-01 13.949400000000000000 1997-01-01 13.174400000000000000 1998-01-01 12.248100000000000000 1999-01-01 11.669700000000000000 2000-01-01 12.088800000000000000 2001-01-01 12.513600000000000000 2002-01-01 10.703100000000000000 2003-01-01 9.009640000000000000 2004-01-01 7.972270000000000000 2005-01-01 8.621290000000000000 2006-01-01 7.300680000000001000 2007-01-01 5.207350000000000000 2008-01-01 6.299150000000000000 2009-01-01 7.250530000000000000 2010-01-01 6.177450000000000000 2011-01-01 5.707540000000000000 2012-01-01 7.466289999999999000 2013-01-01 7.837980000000000000 2014-01-01 5.632650000000000000 2015-01-01 4.141850000000000000 2016-01-01 3.589819999999999600