| Year | Value | | 2022 | 22.188392157513 | | 2021 | 19.609238744781 | | 2020 | 15.706721872422 | | 2019 | 10.221623158481 | | 2018 | 15.553575766877 | | 2017 | 17.178457907419 | | 2016 | 17.874965362826 | | 2015 | 18.453777428733 | | 2014 | 13.281257221045 | | 2013 | 14.836719782724 | | 2012 | 14.096732790692 | | 2011 | 11.095722762862 | | 2010 | 13.200763048602 | | 2009 | 14.047556655862 | | 2008 | 27.904920347991 | | 2007 | 28.600692629381 | | 2006 | 28.544833032934 | | 2005 | 24.307317917496 | | 2004 | 19.714835101296 | | 2003 | 16.341811815504 | | 2002 | 10.245405828021 | | 2001 | 5.4119836308568 | | 2000 | 0.92701687966336 | | 1999 | 2.8340555504993 | | 1998 | 0.75617430764904 | | 1997 | 3.9141126068108 | | 1996 | 1.7875888339849 | | 1995 | -2.1299177533343 | | 1994 | 2.5688297783348 | | 1993 | -5.4394081804519 |
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