Year Percent 1997-01-01 3.4095199999999997 1998-01-01 3.3177199999999996 1999-01-01 3.1158900000000003 2000-01-01 3.6527199999999995 2001-01-01 4.2751300000000000 2002-01-01 4.2751300000000000 2003-01-01 4.2751300000000000 2004-01-01 4.2751300000000000 2005-01-01 4.2751300000000000 2006-01-01 4.2751300000000000 2007-01-01 2.8835300000000000 2008-01-01 2.4682800000000000 2009-01-01 2.7871000000000000 2010-01-01 2.2945200000000000 2011-01-01 1.8684200000000000 2012-01-01 1.7394900000000002 2013-01-01 3.5033100000000000 2014-01-01 9.0642300000000000 2015-01-01 14.4825000000000000 2016-01-01 14.5435000000000000