Year Percent 1960-01-01 7.5846100000000005 1961-01-01 7.4046699999999990 1962-01-01 8.1620200000000000 1963-01-01 8.2431700000000000 1964-01-01 7.0152000000000000 1965-01-01 6.4346500000000000 1966-01-01 6.4202600000000000 1967-01-01 6.6731200000000000 1968-01-01 6.8187300000000000 1969-01-01 7.4503500000000000 1970-01-01 9.2641600000000000 1971-01-01 9.8992300000000010 1972-01-01 9.7528100000000000 1973-01-01 11.6991000000000000 1974-01-01 12.7373000000000000 1975-01-01 12.3616000000000000 1976-01-01 13.7718000000000000 1977-01-01 16.5597000000000000 1978-01-01 18.7404000000000000 1979-01-01 18.5410000000000000 1980-01-01 16.2309999999999980 1981-01-01 14.8666000000000000 1982-01-01 15.4478000000000000 1983-01-01 17.0727000000000000 1984-01-01 16.7765000000000000 1985-01-01 16.0117000000000000 1986-01-01 15.0927000000000000 1987-01-01 14.5415000000000000 1988-01-01 15.5394000000000000 1989-01-01 15.9863000000000000 1990-01-01 16.6473000000000000 1991-01-01 16.4509000000000000 1992-01-01 17.1925000000000000 1993-01-01 15.9518000000000000 1994-01-01 14.3803000000000000 1995-01-01 13.6348000000000000 1996-01-01 14.5402000000000000 1997-01-01 15.4873000000000000 1998-01-01 15.1591000000000000 1999-01-01 15.7189000000000000 2000-01-01 17.0883000000000000 2001-01-01 18.0765000000000000 2002-01-01 19.4709000000000000 2003-01-01 21.2963000000000000 2004-01-01 23.7602000000000000 2005-01-01 24.5819000000000000 2006-01-01 24.8907000000000000 2007-01-01 25.4325000000000000 2008-01-01 25.2392000000000000 2009-01-01 26.4725000000000000 2010-01-01 28.7688000000000000 2011-01-01 30.0031000000000000 2012-01-01 30.1296000000000000 2013-01-01 32.4443000000000000 2014-01-01 34.4737000000000000 2015-01-01 36.1639000000000000 2016-01-01 36.1777000000000000