Year Percent 1991-01-01 0.1882080000000000 1992-01-01 0.2311320000000000 1993-01-01 1.1095500000000000 1994-01-01 1.6824800000000000 1995-01-01 1.7531100000000000 1996-01-01 1.6992000000000000 1997-01-01 2.4859700000000000 1998-01-01 2.4491800000000000 1999-01-01 1.8903700000000000 2000-01-01 1.4517200000000001 2001-01-01 1.7999900000000002 2002-01-01 1.6824200000000000 2003-01-01 1.4372400000000000 2004-01-01 1.7100700000000000 2005-01-01 1.9603700000000002 2006-01-01 2.0607100000000000 2007-01-01 3.4401800000000002 2008-01-01 4.1097000000000000 2009-01-01 3.5766400000000003 2010-01-01 3.5742900000000000 2011-01-01 3.9235900000000004 2012-01-01 3.3819400000000000 2013-01-01 2.5234000000000000 2014-01-01 3.1096500000000000 2015-01-01 3.7711699999999997 2016-01-01 3.2047500000000000 2017-01-01 2.9542400000000000