Year Percent 1965-01-01 0.25249699999999997 1966-01-01 0.56091000000000000 1967-01-01 0.83851500000000000 1968-01-01 1.21894000000000000 1969-01-01 1.80810000000000000 1970-01-01 0.76533600000000000 1971-01-01 0.35936900000000000 1972-01-01 0.65019300000000000 1973-01-01 0.95406499999999990 1974-01-01 0.85130500000000000 1975-01-01 2.66807000000000000 1976-01-01 4.42106999999999900 1977-01-01 3.85425000000000000 1978-01-01 3.36821999999999950 1979-01-01 5.16669000000000000 1980-01-01 4.72463000000000000 1981-01-01 7.03222000000000000 1982-01-01 9.79236000000000000 1983-01-01 10.81610000000000000 1984-01-01 10.04350000000000000 1985-01-01 9.20554000000000000 1986-01-01 10.45030000000000000 1987-01-01 11.52880000000000000 1988-01-01 9.49998000000000000 1989-01-01 7.73487000000000000 1990-01-01 7.22670000000000000 1991-01-01 5.28404000000000000 1992-01-01 6.72209000000000000 1993-01-01 6.22653000000000000 1994-01-01 6.50483000000000000 1995-01-01 4.04876000000000000 1996-01-01 1.93652000000000000 1997-01-01 1.28302000000000000 1998-01-01 2.35207000000000000 1999-01-01 2.61322000000000000 2000-01-01 1.10233999999999990 2001-01-01 1.52014000000000000 2002-01-01 3.60722000000000000 2003-01-01 4.47918000000000000 2004-01-01 4.39953000000000000 2005-01-01 4.80168000000000000 2006-01-01 3.46426999999999950 2007-01-01 3.00454000000000000 2008-01-01 7.19086999999999900 2009-01-01 11.16940000000000000 2010-01-01 10.14830000000000000 2011-01-01 9.66828999999999900 2012-01-01 9.39857000000000000 2013-01-01 7.92639000000000000 2014-01-01 5.94850000000000000 2015-01-01 4.52157000000000000 2016-01-01 7.87211000000000000