Year maximum value in 2004 = 100 2006 7.9181790965 2007 6.9680775942 2008 8.2281114609 2009 8.0150212972 2010 10.1315293537 2011 7.1812516046 2012 7.4785204289 2013 7.912639869 2014 7.6057603609 2015 7.2254263727 2016 8.9323175548 2017 8.2984627294 2018 8.05733974 2019 7.5310401283 2020 8.0065223588 2021 7.0170927504