Year Percent 1998-01-01 0.059757000000000005 1999-01-01 0.142535000000000000 2000-01-01 0.169027999999999980 2001-01-01 0.145472000000000000 2002-01-01 0.138016000000000000 2003-01-01 0.137273000000000000 2004-01-01 0.174889000000000020 2005-01-01 0.175123000000000000 2006-01-01 0.188836000000000000 2007-01-01 0.232096000000000000 2008-01-01 0.251107000000000000 2009-01-01 0.267014000000000000 2010-01-01 0.285888000000000030 2011-01-01 0.297257999999999970 2012-01-01 0.312571000000000000 2013-01-01 0.353930000000000000 2014-01-01 0.406006000000000000 2015-01-01 0.451162000000000000