| Year | Value | | 2022 | 16.819282387188 | | 2021 | 12.556590093727 | | 2020 | 12.219560426771 | | 2019 | 12.285006723502 | | 2018 | 13.622164546266 | | 2017 | 16.863610303341 | | 2016 | 19.732085269227 | | 2015 | 21.457078490292 | | 2014 | 9.9016230559923 | | 2013 | 7.8864745638709 | | 2012 | 12.298114880995 | | 2011 | 11.722376410229 | | 2010 | 13.94410294846 | | 2009 | 12.070582892839 | | 2008 | 16.208772749311 | | 2007 | 20.20712788874 | | 2006 | 19.403390688438 | | 2005 | 21.933385230416 | | 2004 | 27.904745709619 | | 2003 | 23.911806382434 | | 2002 | 23.871722338962 | | 2001 | 21.886008097549 | | 2000 | 20.930412872456 | | 1999 | 22.452694110792 | | 1998 | 18.330679621417 | | 1997 | 18.787762662668 | | 1996 | 19.978869001092 | | 1995 | 23.40627981808 | | 1994 | 32.270299625593 |
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