Year maximum value in 2004 = 100 2006 17.5269521879 2007 17.0637534565 2008 19.1098528283 2009 22.0647736757 2010 22.4122789396 2011 28.9990470286 2012 28.4174462947 2013 28.5912329011 2014 29.0461566607 2015 29.8715693776 2016 34.7454587829 2017 35.8537436825 2018 36.1605769121 2019 36.7149125003 2020 36.215161659 2021 36.2862939823