| Year | Value | | 2022 | 40.972427120077 | | 2021 | 46.760978543038 | | 2020 | 46.062331294412 | | 2019 | 51.695787736528 | | 2018 | 36.410123016741 | | 2017 | 24.249720196174 | | 2016 | 28.397661953608 | | 2015 | 26.96006418847 | | 2014 | 23.855904887978 | | 2013 | 20.704875806886 | | 2012 | 14.847016230661 | | 2011 | 18.854452652303 | | 2010 | 17.796439856042 | | 2009 | 22.762540551274 | | 2008 | 32.155768322699 | | 2007 | 22.459495065187 | | 2006 | 24.068944067735 | | 2005 | 18.060081333304 | | 2004 | 15.962002752193 | | 2003 | 12.619635590454 | | 2002 | 12.433191109045 | | 2001 | 8.2562309229791 | | 2000 | 6.088196643684 | | 1999 | 0.30958183592554 | | 1998 | 0.29666302151199 | | 1997 | 15.401717918077 | | 1996 | 5.6236960811864 | | 1995 | 13.831436531256 | | 1994 | 14.274655545683 | | 1993 | 15.798081170383 | | 1992 | 15.072395802167 | | 1991 | 21.293019157352 | | 1990 | 26.803071259545 | | 1989 | 20.22544683633 | | 1988 | 14.799848520531 | | 1987 | 19.483580019073 | | 1986 | 13.89821005213 | | 1985 | 15.464235926063 | | 1984 | 22.828622884412 | | 1983 | 15.14783666673 |
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