Year maximum value in 2004 = 100 2006 31.3788611969 2007 30.944133504 2008 34.6497459388 2009 32.4996176217 2010 36.8622121965 2011 38.5225012776 2012 38.4062703422 2013 39.3915348429 2014 40.0565760249 2015 46.7216813463 2016 44.4227701304 2017 45.0349544405 2018 45.184283328 2019 49.0962441615 2020 48.4002409425 2021 47.2803765363