Year Percent 1982-01-01 0.22475200000000000 1983-01-01 0.19460100000000000 1984-01-01 0.16364500000000000 1985-01-01 0.20681400000000000 1986-01-01 0.24200600000000000 1987-01-01 0.28657800000000000 1988-01-01 0.27186500000000000 1989-01-01 0.23028700000000000 1990-01-01 0.21317700000000000 1991-01-01 0.21358000000000002 1992-01-01 0.21358000000000002 1993-01-01 0.21358000000000002 1994-01-01 0.21358000000000002 1995-01-01 0.21358000000000002 1996-01-01 0.21358000000000002 1997-01-01 0.25959600000000000 1998-01-01 0.60150500000000010 1999-01-01 0.61092100000000000 2000-01-01 0.37535799999999997 2001-01-01 0.40107100000000000 2002-01-01 2.02780999999999970 2003-01-01 1.85945000000000000 2004-01-01 1.99327000000000000 2005-01-01 1.78507000000000020 2006-01-01 1.49380000000000000 2007-01-01 2.51099000000000000 2008-01-01 2.00698000000000000 2009-01-01 2.71917999999999970 2010-01-01 3.99451999999999960 2011-01-01 5.03326000000000000 2012-01-01 6.14124000000000000 2013-01-01 7.56858999999999950 2014-01-01 9.33279000000000000 2015-01-01 11.12540000000000000 2016-01-01 12.77730000000000000