| Year | Value | | 2022 | 7.1957888597581 | | 2021 | 2.2045720475741 | | 2020 | 3.313322895445 | | 2019 | 2.867588034469 | | 2018 | 2.6160119095227 | | 2017 | 5.2097170591421 | | 2016 | 5.7063750461621 | | 2015 | 5.5896860625173 | | 2014 | 3.0757066895864 | | 2013 | 4.9052087569456 | | 2012 | 12.679037722466 | | 2011 | 16.564349617452 | | 2010 | 3.9765528847817 | | 2009 | 13.017256188919 | | 2008 | 12.050855548289 | | 2007 | 6.1385108328505 | | 2006 | 7.3106761356186 | | 2005 | 8.4487264229953 | | 2004 | 3.7212874397823 | | 2003 | 8.6804765156688 | | 2002 | 0.2875085117652 | | 2001 | 1.8651252408477 | | 2000 | 3.39202158513 | | 1999 | 5.777368986879 | | 1998 | 0.068804171998317 | | 1997 | 8.1690214410696 | | 1996 | 7.1916466043334 | | 1995 | 6.5501401897037 | | 1994 | 10.036759879218 |
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