Year % 2000 23.93870319458033 2001 23.929125994660676 2002 23.79058118792261 2003 23.712391252177873 2004 23.404563706942184 2005 23.046265308353856 2006 22.86613147988889 2007 22.569152999431246 2008 22.41409016953569 2009 22.265735030000855 2010 21.951154262100857 2011 21.626735577611793 2012 21.771903683351784 2013 21.417899186014075 2014 21.417238548238593 2015 21.669282536340322 2016 21.302073392193808 2017 20.94504146838811 2018 20.919369369375058 2019 20.82222804455745