Year Percent 1980-01-01 0.22048500000000000 1981-01-01 0.23524400000000000 1982-01-01 0.31336100000000000 1983-01-01 0.47090900000000000 1984-01-01 0.98196100000000010 1985-01-01 1.46858000000000000 1986-01-01 0.65243600000000000 1987-01-01 0.46965400000000000 1988-01-01 0.31284000000000000 1989-01-01 0.18707900000000000 1990-01-01 0.33133500000000000 1991-01-01 0.49532600000000004 1992-01-01 1.16448000000000000 1993-01-01 2.61372000000000030 1994-01-01 3.17856000000000000 1995-01-01 3.54150999999999970 1996-01-01 3.68416000000000000 1997-01-01 4.13305999999999950 1998-01-01 4.87692000000000000 1999-01-01 4.18433000000000000 2000-01-01 4.15865000000000000 2001-01-01 3.78760000000000000 2002-01-01 4.21185000000000000 2003-01-01 4.22719000000000000 2004-01-01 4.17293000000000000 2005-01-01 3.38783000000000000 2006-01-01 3.88126999999999980 2007-01-01 3.49036999999999950 2008-01-01 3.96916999999999960 2009-01-01 5.24589000000000000 2010-01-01 5.37257000000000000 2011-01-01 5.20366000000000000 2012-01-01 5.15814000000000000 2013-01-01 4.56500000000000000 2014-01-01 3.96610000000000000 2015-01-01 3.13754000000000000 2016-01-01 2.73110000000000000