Year Percent 1976-01-01 0.9639940000000000 1977-01-01 1.2033300000000000 1978-01-01 1.6818700000000000 1979-01-01 1.6010200000000000 1980-01-01 2.1121800000000000 1981-01-01 3.8983700000000000 1982-01-01 7.8796899999999990 1983-01-01 9.3780200000000000 1984-01-01 7.1704100000000000 1985-01-01 6.0344400000000000 1986-01-01 7.5842300000000010 1987-01-01 6.7472400000000000 1988-01-01 7.8554900000000000 1989-01-01 7.1783899999999990 1990-01-01 7.1783899999999990 1991-01-01 16.4251000000000000 1992-01-01 10.4325000000000000 1993-01-01 8.0462200000000000 1994-01-01 5.4575200000000000 1995-01-01 4.1337100000000000 1996-01-01 3.7283500000000000 1997-01-01 3.8716600000000000 1998-01-01 4.5826300000000000 1999-01-01 4.1546600000000000 2000-01-01 3.2537900000000000 2001-01-01 5.5509699999999995 2002-01-01 7.7004600000000005 2003-01-01 7.5328600000000000 2004-01-01 6.8686700000000000 2005-01-01 6.3786500000000000 2006-01-01 6.6943000000000000 2007-01-01 6.6296100000000004 2008-01-01 5.8981000000000000 2009-01-01 7.0775700000000000 2010-01-01 5.1111900000000010 2011-01-01 3.6252100000000000 2012-01-01 3.0650100000000000 2013-01-01 2.6557000000000000 2014-01-01 2.4538599999999997 2015-01-01 3.1413800000000000 2016-01-01 3.5223400000000002