Year Percent 1960-01-01 0.14286300000000002 1961-01-01 0.17062300000000000 1962-01-01 0.20135600000000000 1963-01-01 0.31310300000000000 1964-01-01 0.43833999999999995 1965-01-01 0.56653100000000000 1966-01-01 0.76952800000000000 1967-01-01 1.14904000000000000 1968-01-01 1.18372000000000000 1969-01-01 0.99468200000000000 1970-01-01 0.88585700000000000 1971-01-01 0.83262099999999990 1972-01-01 0.87378600000000010 1973-01-01 1.04356000000000000 1974-01-01 1.01085000000000000 1975-01-01 1.23312000000000000 1976-01-01 1.19537999999999990 1977-01-01 1.02330000000000000 1978-01-01 0.99312400000000000 1979-01-01 1.11114000000000000 1980-01-01 2.07802000000000000 1981-01-01 1.98785000000000000 1982-01-01 1.99298000000000000 1983-01-01 3.66676999999999960 1984-01-01 4.91971000000000000 1985-01-01 4.37919000000000000 1986-01-01 2.92969000000000030 1987-01-01 2.33694000000000020 1988-01-01 2.10457000000000030 1989-01-01 1.65835000000000000 1990-01-01 1.65822999999999990 1991-01-01 1.49020000000000000 1992-01-01 0.80605799999999990 1993-01-01 0.73129600000000010 1994-01-01 0.79537200000000010 1995-01-01 0.89858900000000000 1996-01-01 3.29690000000000000 1997-01-01 5.34417000000000000 1998-01-01 6.12920000000000000 1999-01-01 6.93341000000000000 2000-01-01 7.31650000000000000 2001-01-01 7.93673000000000100 2002-01-01 4.57913000000000000 2003-01-01 1.83410000000000000 2004-01-01 1.54597000000000000 2005-01-01 1.30469000000000000 2006-01-01 1.02352999999999980 2007-01-01 0.87049400000000010 2008-01-01 0.63470300000000000 2009-01-01 0.50466099999999990 2010-01-01 0.41432100000000000 2011-01-01 0.31167200000000000 2012-01-01 0.28473100000000000 2013-01-01 0.28473000000000004 2014-01-01 0.26909099999999997 2015-01-01 0.23161500000000002 2016-01-01 0.28960300000000000