Year Percent 1960-01-01 1.4198700000000000 1961-01-01 1.2970700000000002 1962-01-01 1.1346700000000000 1963-01-01 0.9585799999999999 1964-01-01 0.8563850000000001 1965-01-01 0.7832319999999999 1966-01-01 0.7674979999999999 1967-01-01 0.6775710000000000 1968-01-01 0.5735680000000001 1969-01-01 0.5456770000000001 1970-01-01 0.8376780000000000 1971-01-01 1.2736100000000001 1972-01-01 1.3496100000000000 1973-01-01 1.3303800000000000 1974-01-01 1.0131400000000000 1975-01-01 1.7621500000000000 1976-01-01 2.7068700000000000 1977-01-01 2.9565799999999998 1978-01-01 4.3450100000000000 1979-01-01 4.4659699999999996 1980-01-01 4.1740100000000000 1981-01-01 5.0758700000000000 1982-01-01 6.0872000000000000 1983-01-01 8.6870400000000000 1984-01-01 11.2375000000000000 1985-01-01 13.7770000000000010 1986-01-01 13.6401000000000000 1987-01-01 12.5340000000000000 1988-01-01 12.7613000000000000 1989-01-01 11.7115000000000000 1990-01-01 10.3467000000000000 1991-01-01 11.1011000000000000 1992-01-01 12.2415000000000000 1993-01-01 12.6610000000000000 1994-01-01 12.5278000000000000 1995-01-01 14.1966000000000000 1996-01-01 13.1436000000000000 1997-01-01 12.2346000000000000 1998-01-01 12.2157000000000000 1999-01-01 11.2709999999999990 2000-01-01 11.1667000000000000 2001-01-01 11.3980000000000000 2002-01-01 11.5279000000000000 2003-01-01 10.6389000000000000 2004-01-01 9.3218800000000000 2005-01-01 6.9712800000000000 2006-01-01 5.5678700000000000 2007-01-01 4.5038900000000000 2008-01-01 3.2513300000000000 2009-01-01 3.9292500000000000 2010-01-01 3.0839200000000000 2011-01-01 2.4103100000000000 2012-01-01 2.4103100000000000 2013-01-01 2.4103100000000000 2014-01-01 31.3788000000000000