Year maximum value in 2004 = 100 2006 16.9899724474 2007 18.8605260592 2008 17.8926232165 2009 21.9902567564 2010 21.1939612293 2011 23.4837069364 2012 20.4743058158 2013 19.8683943893 2014 23.0616073862 2015 26.4680884035 2016 25.4679334608 2017 26.7451620594 2018 34.4720594303 2019 33.3289967746 2020 33.9681172217 2021 33.8591078945