| Year | Value | | 2022 | 28.737297676623 | | 2021 | 5.1064112900284 | | 2020 | 3.7659712224536 | | 2019 | 4.8377835142871 | | 2018 | 3.0450539733708 | | 2017 | 6.570229974556 | | 2016 | 6.3593089803794 | | 2015 | 9.6762403310186 | | 2014 | 5.0887855462588 | | 2013 | 4.5978789736313 | | 2012 | 4.546334273553 | | 2011 | 7.6872510335618 | | 2010 | 7.4838508635085 | | 2009 | 0.062718596710879 | | 2008 | 12.783047261882 | | 2007 | 12.36716684143 | | 2006 | 12.777755783035 | | 2005 | 11.959183722213 | | 2004 | 12.524276842823 | | 2003 | 11.746079205823 | | 2002 | 5.301243902616 | | 2001 | 9.7646628575763 | | 2000 | 31.299301581779 | | 1999 | 39.255980689175 | | 1998 | 7.695765175172 | | 1997 | 11.772832449447 | | 1996 | 23.505677296337 | | 1995 | 29.865610409572 | | 1994 | 486.42562379589 | | 1993 | 1,613.6039887619 | | 1992 | 1,026.826264247 |
|