Year Number 2003 0.556768476963043 2004 0.330648332834244 2005 0.332869827747345 2006 0.331756144762039 2007 0.308105289936066 2008 0.309818059206009 2009 0.323601871728897 2010 0.320087254047394 2011 0.306695103645325 2012 0.282746523618698 2013 0.297252923250198 2014 0.238057717680931 2015 0.249322980642319 2016 0.253411799669266 2017 0.263454109430313 2018 0.257120162248611 2019 0.252529382705688 2020 0.247384041547775 2021 0.251843899488449 2022 0.260167717933655