Year Percent 1960-01-01 3.70000000000000000 1961-01-01 3.75000000000000000 1962-01-01 3.80000000000000000 1963-01-01 1.97500000000000000 1964-01-01 1.41667000000000000 1965-01-01 1.26250000000000000 1966-01-01 1.37000000000000000 1967-01-01 1.57500000000000000 1968-01-01 1.91429000000000000 1969-01-01 2.99375000000000000 1970-01-01 3.17667999999999970 1971-01-01 1.53705000000000000 1972-01-01 0.61836000000000000 1973-01-01 0.74589900000000000 1974-01-01 0.91762199999999990 1975-01-01 0.67573900000000000 1976-01-01 0.93627500000000000 1977-01-01 1.81408000000000000 1978-01-01 2.18412000000000000 1979-01-01 2.18467000000000000 1980-01-01 2.48291000000000000 1981-01-01 2.70995000000000000 1982-01-01 1.88585000000000000 1983-01-01 1.00190000000000000 1984-01-01 0.56046900000000000 1985-01-01 0.27575700000000003 1986-01-01 0.29462000000000000 1987-01-01 0.26050400000000000 1988-01-01 0.18566400000000002 1989-01-01 0.20438900000000002 1990-01-01 0.06091799999999999 1991-01-01 0.08516599999999999 1992-01-01 0.14694600000000000 1993-01-01 0.22136399999999998 1994-01-01 0.27668000000000004 1995-01-01 0.29245200000000000 1996-01-01 0.28703600000000000 1997-01-01 0.33558200000000000 1998-01-01 0.46195800000000000 1999-01-01 0.65509700000000000 2000-01-01 0.70656000000000010 2001-01-01 0.67896400000000000 2002-01-01 0.51212100000000000 2003-01-01 0.34754800000000000 2004-01-01 0.26937800000000000 2005-01-01 0.25365800000000000 2006-01-01 0.30913300000000000 2007-01-01 0.41111200000000000 2008-01-01 0.44760600000000006 2009-01-01 0.44536800000000004 2010-01-01 0.36608500000000000 2011-01-01 0.39864200000000000 2012-01-01 0.46976999999999997 2013-01-01 0.48603199999999996 2014-01-01 0.38694700000000000 2015-01-01 0.31721700000000000 2016-01-01 0.35070000000000000