Year % 2000 17.567820589227566 2001 17.294641264141525 2002 17.115437227367547 2003 17.028945302192582 2004 16.950043490158663 2005 16.893869268889095 2006 16.829232995242425 2007 16.795380629976396 2008 16.732697936195063 2009 16.702794630419017 2010 16.629586871034245 2011 16.68654842740123 2012 16.73969777831221 2013 16.864050479341824 2014 16.97804596789172 2015 17.128257551149527 2016 17.29332541747874 2017 17.46074918647122 2018 17.61051537800156 2019 17.7494354754638