Year Number 2006 0.0475496053695679 2007 0.108533091843128 2008 0.767700612545013 2009 0.817372143268585 2010 0.584210991859436 2011 0.565341532230377 2012 0.596563041210175 2013 0.504595458507538 2014 0.219455271959305 2015 0.136638209223747 2016 0.268716216087341 2017 -0.062578022480011 2018 0.0375925563275814 2019 0.0580168217420578 2020 -0.0612264648079872 2021 -0.0525020584464073 2022 -0.0591769814491272