| Year | Value | | 2022 | 68.15555579967 | | 2021 | 68.173638518952 | | 2020 | 69.640053595614 | | 2019 | 68.172211325172 | | 2018 | 68.500535274884 | | 2017 | 68.720283421257 | | 2016 | 68.468567259268 | | 2015 | 68.033134384869 | | 2014 | 67.815887243431 | | 2013 | 67.083214733532 | | 2012 | 67.030998914946 | | 2011 | 66.345588215578 | | 2010 | 66.604415558876 | | 2009 | 65.691497337236 | | 2008 | 66.397971344872 | | 2007 | 65.56997698416 | | 2006 | 65.266687278314 | | 2005 | 64.410866612287 | | 2004 | 63.239754292857 | | 2003 | 62.811522959523 | | 2002 | 62.844749785054 | | 2001 | 63.44500713159 | | 2000 | 63.877914594855 | | 1999 | 61.724988024385 | | 1998 | 61.148066897113 | | 1997 | 58.772761392912 | | 1996 | 59.648869448152 | | 1995 | 58.455703131501 | | 1994 | 56.530876131628 | | 1993 | 55.243449716617 | | 1992 | 56.102313703573 | | 1991 | 55.857284865677 |
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