Year Percent 1980-01-01 0.59707300000000000 1981-01-01 0.54574700000000000 1982-01-01 0.47243000000000000 1983-01-01 0.50032800000000000 1984-01-01 0.49749399999999994 1985-01-01 0.52795600000000010 1986-01-01 0.79687299999999990 1987-01-01 0.81408800000000000 1988-01-01 0.83520200000000000 1989-01-01 0.88565900000000000 1990-01-01 0.88565900000000000 1991-01-01 0.88565900000000000 1992-01-01 0.88565900000000000 1993-01-01 0.88565900000000000 1994-01-01 0.88565900000000000 1995-01-01 0.88565900000000000 1996-01-01 0.88565900000000000 1997-01-01 0.88565900000000000 1998-01-01 1.78124000000000020 1999-01-01 1.58127000000000020 2000-01-01 1.29429000000000000 2001-01-01 2.89065000000000000 2002-01-01 2.82829000000000000 2003-01-01 2.27245999999999970 2004-01-01 1.89940999999999980 2005-01-01 1.57421000000000000 2006-01-01 3.45219000000000030 2007-01-01 6.27495000000000000 2008-01-01 4.77062000000000000 2009-01-01 11.73020000000000000 2010-01-01 9.89618000000000100 2011-01-01 8.60783000000000000 2012-01-01 8.68798000000000000 2013-01-01 8.00213000000000100 2014-01-01 7.32430000000000000 2015-01-01 8.38866000000000000 2016-01-01 12.15090000000000000