Year % 1997 15.62 2000 12.06 2001 12.09 2002 9.14 2003 9.03 2004 8.05 2005 7.3 2006 7.34 2007 6.95 2008 4.8 2009 7.03 2010 7.14 2011 3.79 2012 3.63 2013 3.68 2014 2.7 2015 2.69 2016 2.87 2017 2.95 2018 3.36 2019 3.36 2020 3.17 2021 3.3