Year Percent 1980-01-01 0.5741670000000000 1981-01-01 0.7518760000000000 1982-01-01 1.2374300000000000 1983-01-01 1.9938799999999999 1984-01-01 2.1737900000000003 1985-01-01 2.1555000000000000 1986-01-01 2.5491200000000003 1987-01-01 3.2355700000000000 1988-01-01 4.5282700000000000 1989-01-01 4.1426800000000000 1990-01-01 3.7249100000000000 1991-01-01 2.6150200000000000 1992-01-01 2.5191300000000000 1993-01-01 1.8192599999999999 1994-01-01 2.9507800000000000 1995-01-01 1.4394200000000001 1996-01-01 1.2196700000000000 1997-01-01 1.0009299999999999 1998-01-01 1.1935500000000000 1999-01-01 1.3729100000000000 2000-01-01 1.1750000000000000 2001-01-01 1.1259800000000000 2002-01-01 2.2509900000000003 2003-01-01 1.9953100000000000 2004-01-01 2.1522700000000000 2005-01-01 1.8848000000000000 2006-01-01 1.6532200000000001 2007-01-01 2.2755799999999997 2008-01-01 1.3053000000000000 2009-01-01 1.2121200000000000 2010-01-01 2.6405900000000000 2011-01-01 2.1281500000000000 2012-01-01 1.5658700000000000 2013-01-01 3.1731800000000000 2014-01-01 3.5804600000000000 2015-01-01 5.0615000000000000 2016-01-01 4.4080300000000000