Year % 1982 28.6 1992 26.4 2000 25.9 2002 24.1 2006 26 2007 26.7 2008 26.3 2009 25.7 2010 25.4 2011 24.7 2012 25 2013 25.5 2014 25.5 2015 25.2 2016 25.8 2017 25.5 2018 25.8 2019 26.6 2020 26.4