Year Percent 1960-01-01 1.64214000000000020 1961-01-01 0.94127800000000010 1962-01-01 0.41952399999999995 1963-01-01 0.40375200000000000 1964-01-01 0.45341600000000000 1965-01-01 0.57976500000000000 1966-01-01 0.69503200000000000 1967-01-01 0.51372800000000000 1968-01-01 0.31876700000000000 1969-01-01 0.29389200000000000 1970-01-01 0.18523000000000000 1971-01-01 0.17720600000000000 1972-01-01 0.14104100000000000 1973-01-01 0.16923000000000000 1974-01-01 0.41313800000000000 1975-01-01 0.85598800000000000 1976-01-01 1.38294000000000000 1977-01-01 1.76109000000000000 1978-01-01 2.41215000000000000 1979-01-01 3.17195000000000000 1980-01-01 3.77040000000000000 1981-01-01 3.74356999999999960 1982-01-01 4.63500000000000000 1983-01-01 7.11198000000000000 1984-01-01 8.49371000000000000 1985-01-01 9.27122000000000000 1986-01-01 10.04810000000000000 1987-01-01 9.21082000000000000 1988-01-01 7.68617000000000000 1989-01-01 8.03108999999999900 1990-01-01 8.68942000000000000 1991-01-01 7.85323000000000000 1992-01-01 6.65159000000000000 1993-01-01 6.63057000000000000 1994-01-01 6.09795000000000000 1995-01-01 6.73841000000000100 1996-01-01 7.22073999999999900 1997-01-01 6.85788000000000100 1998-01-01 6.99306000000000100 1999-01-01 6.07365000000000000 2000-01-01 5.69359000000000000 2001-01-01 4.94832000000000000 2002-01-01 4.96810000000000000 2003-01-01 3.93294000000000030 2004-01-01 2.49102000000000020 2005-01-01 2.71387000000000000 2006-01-01 2.69650000000000000 2007-01-01 3.01080000000000000 2008-01-01 3.15863000000000000 2009-01-01 2.70012000000000000 2010-01-01 2.76374000000000030 2011-01-01 2.72448000000000000 2012-01-01 2.27904000000000000 2013-01-01 1.81415999999999980 2014-01-01 1.50197999999999990 2015-01-01 1.17557999999999980 2016-01-01 0.96412700000000010