Year maximum value in 2004 = 100 2006 18.6136384247 2007 19.178253195 2008 18.446054048 2009 22.5490367922 2010 22.2761455032 2011 25.3045380203 2012 27.440455093 2013 26.5834499055 2014 29.9790611252 2015 28.2729691385 2016 29.8976744985 2017 30.8657480405 2018 30.5488209387 2019 31.2282136175 2020 31.5878780135 2021 35.188239069