Year Percent 1973-01-01 0.1427790000000000 1974-01-01 0.1492240000000000 1975-01-01 0.0732120000000000 1976-01-01 0.0728710000000000 1977-01-01 3.5458900000000000 1978-01-01 3.7013100000000000 1979-01-01 5.4926300000000000 1980-01-01 6.0853900000000000 1981-01-01 7.6747000000000000 1982-01-01 10.5837000000000000 1983-01-01 10.4250000000000000 1984-01-01 10.6847000000000000 1985-01-01 11.6696000000000000 1986-01-01 11.3792000000000000 1987-01-01 11.2732000000000000 1988-01-01 11.4655000000000000 1989-01-01 12.0497000000000000 1990-01-01 12.1058000000000000 1991-01-01 13.0322000000000000 1992-01-01 13.6839000000000000 1993-01-01 14.7126000000000000 1994-01-01 17.7104000000000000 1995-01-01 17.7756000000000000 1996-01-01 15.4403000000000000 1997-01-01 15.4403000000000000 1998-01-01 14.7088000000000000 1999-01-01 11.7791000000000000 2000-01-01 13.3791000000000000 2001-01-01 11.1728000000000000 2002-01-01 11.4815000000000000 2003-01-01 8.5312300000000000 2004-01-01 5.0170900000000005 2005-01-01 5.9625200000000000 2006-01-01 6.9892600000000010 2007-01-01 7.3919000000000000 2008-01-01 8.1342400000000000 2009-01-01 9.5607500000000000 2010-01-01 10.4323000000000000 2011-01-01 11.1774000000000000 2012-01-01 13.7964000000000000 2013-01-01 16.0687000000000000 2014-01-01 17.2074000000000000 2015-01-01 17.2425000000000000 2016-01-01 16.7408000000000000