Year Number 1996 0.59960013628006 1998 0.620563447475433 2000 0.725428760051727 2002 0.67558491230011 2003 0.764780938625336 2004 0.510814487934113 2005 0.40130627155304 2006 0.171267151832581 2007 0.312711805105209 2008 0.360625088214874 2009 0.117766954004765 2010 0.0599887408316135 2011 -0.00103536900132895 2012 0.0581903122365475 2013 0.167196571826935 2014 0.250029027462006 2015 0.337751358747482 2016 0.287313491106033 2017 0.169449850916862 2018 0.281118184328079 2019 0.251167297363281 2020 0.238317847251892 2021 0.303267598152161 2022 0.460202544927597