| Year | Value | | 2021 | 8.0423206278028 | | 2020 | 6.7715458276333 | | 2019 | 5.2454767960839 | | 2018 | 6.0191309657068 | | 2017 | 7.4400043732574 | | 2016 | 14.546023794615 | | 2015 | 6.6657761154155 | | 2014 | 6.7065782909272 | | 2013 | 5.8464091732046 | | 2012 | 5.0979148497582 | | 2011 | 8.4248876191979 | | 2010 | 7.4004635674212 | | 2009 | 7.3160785828857 | | 2008 | 17.139899777207 | | 2007 | 10.846836207556 | | 2006 | 8.7216938609175 | | 2005 | 7.5799992912576 | | 2004 | 6.882054389819 | | 2003 | 6.4382181011894 | | 2002 | 5.8369245210564 | | 2001 | 8.3541377716134 | | 2000 | 13.180890586573 | | 1999 | 8.2960276534257 | | 1998 | 7.1463266545233 | | 1997 | 17.408041060736 | | 1996 | 39.182542365411 | | 1995 | 176.15529894237 | | 1994 | 1,877.3723951757 |
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