Year Percent 1960-01-01 14.3577000000000000 1961-01-01 13.8802000000000000 1962-01-01 13.6842000000000000 1963-01-01 13.6899000000000000 1964-01-01 12.7990000000000010 1965-01-01 13.2881000000000000 1966-01-01 14.0867000000000000 1967-01-01 14.7667000000000000 1968-01-01 13.3131000000000000 1969-01-01 13.5235000000000000 1970-01-01 13.2051000000000000 1971-01-01 14.3336000000000000 1972-01-01 15.7344000000000000 1973-01-01 12.5270000000000010 1974-01-01 8.3312300000000000 1975-01-01 7.6957600000000010 1976-01-01 8.3702800000000010 1977-01-01 9.8107899999999990 1978-01-01 11.7858000000000000 1979-01-01 13.0792000000000000 1980-01-01 13.1699000000000000 1981-01-01 12.7381000000000000 1982-01-01 13.0337000000000000 1983-01-01 13.1738000000000000 1984-01-01 12.2201000000000000 1985-01-01 11.7718000000000000 1986-01-01 11.9075000000000000 1987-01-01 12.2237000000000000 1988-01-01 11.1074000000000000 1989-01-01 10.7736000000000000 1990-01-01 11.3242000000000000 1991-01-01 11.3127000000000000 1992-01-01 10.9988000000000000 1993-01-01 11.2377000000000000 1994-01-01 10.3512000000000000 1995-01-01 9.7155000000000000 1996-01-01 10.3867000000000000 1997-01-01 9.7148000000000000 1998-01-01 9.5461700000000000 1999-01-01 11.7818000000000000 2000-01-01 13.5723000000000000 2001-01-01 11.2829000000000000 2002-01-01 7.2537300000000000 2003-01-01 3.7887800000000005 2004-01-01 4.3540600000000000 2005-01-01 6.8179399999999990 2006-01-01 7.0052800000000000 2007-01-01 6.4552500000000000 2008-01-01 9.7093100000000000 2009-01-01 11.0192000000000000 2010-01-01 10.3291000000000000 2011-01-01 8.7543100000000000 2012-01-01 8.2932899999999990 2013-01-01 10.4664000000000000 2014-01-01 11.5614000000000000 2015-01-01 9.2983800000000000 2016-01-01 9.2285800000000010