Year Percent 1997-01-01 0.698388000000000 1998-01-01 2.235530000000000 1999-01-01 21.523000000000003 2000-01-01 21.639100000000000 2001-01-01 20.340900000000000 2002-01-01 19.817100000000000 2003-01-01 17.647800000000000 2004-01-01 14.906100000000000 2005-01-01 11.956500000000000 2006-01-01 11.387600000000000 2007-01-01 10.475600000000000 2008-01-01 8.493590000000000 2009-01-01 10.451400000000000 2010-01-01 9.136770000000000 2011-01-01 8.752089999999999 2012-01-01 9.096969999999999 2013-01-01 8.713830000000000 2014-01-01 10.586100000000000 2015-01-01 12.185400000000000 2016-01-01 14.117100000000000