Year Number 1996 0.613030731678009 1998 0.575733542442322 2000 0.595203697681427 2002 0.518141508102417 2003 0.349641561508179 2004 0.364736646413803 2005 0.384340941905975 2006 0.376439899206162 2007 0.348420560359955 2008 0.350017130374908 2009 0.341262251138687 2010 0.352399289608002 2011 0.360775291919708 2012 0.317384898662567 2013 0.347427368164063 2014 0.29147407412529 2015 0.275287687778473 2016 0.286816298961639 2017 0.309247493743896 2018 0.289012312889099 2019 0.280839860439301 2020 0.27869239449501 2021 0.282457619905472 2022 0.277728617191315