Year maximum value in 2004 = 100 2006 19.1443319766 2007 20.8216983 2008 20.3702899842 2009 20.8613062494 2010 21.8374969244 2011 21.3495519612 2012 23.0452813711 2013 25.9302299627 2014 23.1349493171 2015 25.8463580865 2016 29.932786438 2017 30.2016515526 2018 31.4811601456 2019 30.5055815497 2020 29.2474289842 2021 25.5414998811