Year Percent 1992-01-01 2.40029 1993-01-01 6.56810 1994-01-01 8.12923 1995-01-01 6.28324 1996-01-01 9.28365 1997-01-01 16.84290 1998-01-01 21.37830 1999-01-01 25.83540 2000-01-01 38.09050 2001-01-01 41.63980 2002-01-01 33.87410 2003-01-01 30.23060 2004-01-01 24.69360 2005-01-01 18.74050 2006-01-01 28.05680 2007-01-01 78.40780 2008-01-01 74.20760 2009-01-01 52.31770 2010-01-01 62.28430 2011-01-01 50.94240 2012-01-01 42.07360 2013-01-01 40.27450 2014-01-01 47.70700 2015-01-01 63.81970 2016-01-01 67.28120 2017-01-01 64.99240