Year maximum value in 2004 = 100 2006 24.4174974656 2007 23.8404283548 2008 22.6821781401 2009 22.5667401679 2010 21.8205115098 2011 21.0798474275 2012 22.4870874672 2013 22.7834538203 2014 15.9707384923 2015 14.1687046434 2016 12.9176993303 2017 11.8422914291 2018 12.0288827866 2019 11.1109136137 2020 11.0099952327 2021 7.3642450277