| Year | Value | | 2022 | 40.869878126653 | | 2021 | 40.470749568839 | | 2020 | 40.26181284531 | | 2019 | 40.516624286219 | | 2018 | 40.185026913655 | | 2017 | 39.115534777225 | | 2016 | 38.094159902656 | | 2015 | 39.142466003863 | | 2014 | 40.435168027512 | | 2013 | 42.178145790988 | | 2012 | 42.979047844074 | | 2011 | 44.45541397832 | | 2010 | 44.295507557858 | | 2009 | 48.04915121907 | | 2008 | 49.547196501209 | | 2007 | 49.574392892519 | | 2006 | 51.696613180513 | | 2005 | 55.265350638281 | | 2004 | 56.569297529764 | | 2003 | 56.796832819349 | | 2002 | 58.777691366355 | | 2001 | 60.642855084396 | | 2000 | 63.017283795526 | | 1999 | 67.706079648232 | | 1998 | 68.573420061394 | | 1997 | 69.305989762546 | | 1996 | 69.96604884733 | | 1995 | 70.466072178708 | | 1994 | 70.764659097113 | | 1993 | 71.049481265982 | | 1992 | 71.205987436189 | | 1991 | 71.347557516743 |
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