Year % 1997 3.9198606271777012 1998 3.4936138241923373 1999 3.8791495710555735 2000 3.8817005545286487 2001 3.995560488346279 2002 5.678466076696165 2003 6.014434643143546 2004 6.957217113154747 2005 6.409076970254531 2006 8.632425742574268 2007 8.84900990099011 2008 8.767038413878574 2009 9.085347200978896 2010 10.98317094774136 2011 10.508701472556886 2012 14.167433302667886 2013 16.420064958498735 2014 16.751085383502172 2015 16.901918204849792 2016 17.56715967401147 2017 16.581402347276576 2018 16.937424789410368 2019 16.26865671641793 2020 18.43207660083784 2021 17.021933889403766 2022 17.27781230577998 2023 16.608447126071763