Year Percent 1980-01-01 0.8389380000000000 1981-01-01 1.0268600000000000 1982-01-01 1.5436500000000000 1983-01-01 0.7292330000000000 1984-01-01 0.5616060000000000 1985-01-01 1.4560100000000000 1986-01-01 2.2262100000000000 1987-01-01 1.5914000000000000 1988-01-01 0.4024490000000000 1989-01-01 0.8936569999999999 1990-01-01 0.7802279999999999 1991-01-01 4.8140199999999990 1992-01-01 3.5533900000000003 1993-01-01 3.1045900000000000 1994-01-01 4.2799400000000000 1995-01-01 1.7257900000000002 1996-01-01 2.0650400000000000 1997-01-01 3.1149299999999998 1998-01-01 2.2574099999999997 1999-01-01 2.0118000000000000 2000-01-01 2.6644400000000004 2001-01-01 3.5242400000000003 2002-01-01 3.4087199999999998 2003-01-01 4.1407099999999994 2004-01-01 5.4117600000000000 2005-01-01 9.4240800000000000 2006-01-01 11.3876000000000000 2007-01-01 11.5819000000000000 2008-01-01 10.5241000000000000 2009-01-01 12.0133000000000000 2010-01-01 12.7781000000000000 2011-01-01 13.0262000000000000 2012-01-01 7.3497100000000010 2013-01-01 7.9160500000000000 2014-01-01 8.3552699999999990 2015-01-01 8.3677300000000000 2016-01-01 8.7024800000000000