Year Number 1996 0.616059839725494 1998 0.563318967819214 2000 0.586516797542572 2002 0.643847048282623 2003 0.556768476963043 2004 0.364736646413803 2005 0.384340941905975 2006 0.376439899206162 2007 0.348420560359955 2008 0.350017130374908 2009 0.323601871728897 2010 0.320087254047394 2011 0.360775291919708 2012 0.317384898662567 2013 0.347427368164063 2014 0.261565506458282 2015 0.275287687778473 2016 0.253411799669266 2017 0.263454109430313 2018 0.24618773162365 2019 0.252529382705688 2020 0.247384041547775 2021 0.251843899488449 2022 0.260167717933655