Year Percent 1960-01-01 7.8889200000000000 1961-01-01 6.2660599999999995 1962-01-01 4.6973199999999995 1963-01-01 5.6110800000000000 1964-01-01 6.7192000000000000 1965-01-01 7.9937500000000000 1966-01-01 9.9482100000000010 1967-01-01 12.4345000000000000 1968-01-01 14.6858000000000000 1969-01-01 16.6991000000000000 1970-01-01 19.1311000000000000 1971-01-01 19.8981000000000000 1972-01-01 19.4132000000000000 1973-01-01 19.0964000000000000 1974-01-01 17.9696000000000000 1975-01-01 17.2080000000000000 1976-01-01 17.7089000000000000 1977-01-01 17.9941000000000000 1978-01-01 18.0721000000000000 1979-01-01 17.6033000000000000 1980-01-01 17.8579000000000000 1981-01-01 17.6314000000000000 1982-01-01 18.2786000000000000 1983-01-01 18.2979000000000000 1984-01-01 15.5395000000000000 1985-01-01 13.4703000000000000 1986-01-01 13.1218000000000000 1987-01-01 11.7282000000000000 1988-01-01 12.4616000000000000 1989-01-01 13.5978000000000000 1990-01-01 14.1453000000000000 1991-01-01 14.0314000000000000 1992-01-01 17.4140000000000000 1993-01-01 20.0501000000000000 1994-01-01 23.4708000000000000 1995-01-01 23.5962000000000000 1996-01-01 23.7578000000000000 1997-01-01 25.8441000000000000 1998-01-01 24.3861000000000000 1999-01-01 22.9524000000000000 2000-01-01 23.1209000000000000 2001-01-01 22.8114000000000000 2002-01-01 20.9427000000000000 2003-01-01 16.6620000000000000 2004-01-01 13.7925000000000000 2005-01-01 14.0534000000000000 2006-01-01 13.9342000000000000 2007-01-01 14.8060000000000000 2008-01-01 18.2360000000000000 2009-01-01 25.6048000000000000 2010-01-01 29.5351000000000000 2011-01-01 35.4518000000000000 2012-01-01 40.3787000000000000 2013-01-01 41.1520000000000000 2014-01-01 45.8646000000000000 2015-01-01 52.9485000000000000 2016-01-01 53.8057000000000000