Year Percent 1961-01-01 0.83333300000000000 1962-01-01 0.75980400000000000 1963-01-01 0.79383900000000010 1964-01-01 1.56044000000000000 1965-01-01 1.88272000000000020 1966-01-01 1.88192000000000000 1967-01-01 2.14040999999999970 1968-01-01 2.19614000000000000 1969-01-01 1.88752000000000000 1970-01-01 1.70311000000000000 1971-01-01 1.62988000000000000 1972-01-01 1.65235000000000000 1973-01-01 2.35612000000000000 1974-01-01 2.39574000000000000 1975-01-01 3.10796000000000000 1976-01-01 4.07037000000000000 1977-01-01 4.71639000000000050 1978-01-01 4.71639000000000050 1979-01-01 5.29008000000000100 1980-01-01 3.86976000000000000 1981-01-01 3.65761999999999960 1982-01-01 5.38401000000000000 1983-01-01 7.94051000000000100 1984-01-01 7.94051000000000100 1985-01-01 7.94051000000000100 1986-01-01 7.94051000000000100 1987-01-01 7.94051000000000100 1988-01-01 7.94051000000000100 1989-01-01 7.01758999999999900 1990-01-01 7.09265000000000000 1991-01-01 6.94995000000000000 1992-01-01 8.03619000000000000 1993-01-01 9.23023000000000000 1994-01-01 8.27821000000000100 1995-01-01 7.59003000000000050 1996-01-01 6.90478999999999900 1997-01-01 6.98693000000000000 1998-01-01 9.92566000000000000 1999-01-01 8.38972000000000000 2000-01-01 5.34354000000000000 2001-01-01 7.18578999999999900 2002-01-01 8.16605000000000000 2003-01-01 8.92718000000000000 2004-01-01 7.91666000000000000 2005-01-01 5.93826999999999900 2006-01-01 4.12871999999999950 2007-01-01 4.40837000000000000 2008-01-01 2.20670000000000000 2009-01-01 0.92908899999999990 2010-01-01 0.97686700000000000 2011-01-01 0.53616100000000000 2012-01-01 0.26523800000000003 2013-01-01 0.23967900000000000 2014-01-01 2.66082000000000000 2015-01-01 9.28291000000000100