Year % 1997 15.2 2000 12.05 2001 11.6 2002 8.66 2003 8.44 2004 7.49 2005 7.36 2006 6.72 2007 5.99 2008 1.43 2009 4.72 2010 4.82 2011 0.89 2012 0.7 2013 0.74 2014 0.67 2015 0.66 2016 0.75 2017 0.63 2018 0.77 2019 0.77 2020 0.76 2021 0.78