Year Number 2004 0.376263976097107 2005 0.296854168176651 2006 0.404284834861755 2007 0.440971940755844 2008 0.451515167951584 2009 0.423608183860779 2010 0.449280053377151 2011 0.434491038322449 2012 0.398956000804901 2013 0.38144639134407 2014 0.46657195687294 2015 0.448273360729218 2016 0.43443551659584 2017 0.445859044790268 2018 0.456688791513443 2019 0.461858510971069 2020 0.492229521274567 2021 0.484019696712494 2022 0.47904047369957