Year maximum value in 2004 = 100 2006 23.2622370108 2007 22.2841571525 2008 22.4741442833 2009 23.9974380801 2010 25.7901792911 2011 23.3177928083 2012 30.7808288749 2013 30.0039486071 2014 31.750832033 2015 34.2809212316 2016 37.6500090103 2017 38.5586658414 2018 38.667335723 2019 41.3157463763 2020 41.5863010694 2021 41.4695768989