Year Percent 1981-01-01 0.09574700000000000 1982-01-01 0.14840500000000000 1983-01-01 0.26040700000000000 1984-01-01 0.26835000000000000 1985-01-01 0.17936900000000000 1986-01-01 0.04693400000000000 1987-01-01 0.13871700000000000 1988-01-01 0.54854399999999990 1989-01-01 0.91807400000000000 1990-01-01 0.82540600000000000 1991-01-01 0.56777100000000000 1992-01-01 0.43557299999999993 1993-01-01 0.33752800000000000 1994-01-01 1.41239000000000000 1995-01-01 2.79833000000000000 1996-01-01 3.10160000000000000 1997-01-01 3.67614000000000000 1998-01-01 4.34312000000000000 1999-01-01 4.65405999999999900 2000-01-01 4.66686999999999900 2001-01-01 4.71020000000000000 2002-01-01 5.09169000000000000 2003-01-01 4.96523000000000000 2004-01-01 4.49525000000000000 2005-01-01 3.86666999999999960 2006-01-01 3.17794000000000000 2007-01-01 2.98985999999999970 2008-01-01 2.05903000000000000 2009-01-01 1.26742000000000000 2010-01-01 1.85069000000000020 2011-01-01 2.51934000000000000 2012-01-01 2.53540000000000000 2013-01-01 2.57649000000000000 2014-01-01 3.07552000000000000 2015-01-01 3.34516999999999950 2016-01-01 3.95039000000000000