| Year | Value | | 2022 | 45.998160073597 | | 2021 | 45.998160073597 | | 2020 | 45.551683728396 | | 2019 | 45.019475816712 | | 2018 | 44.717447004247 | | 2017 | 44.719998434105 | | 2016 | 44.710211591536 | | 2015 | 44.718041065591 | | 2014 | 44.710211591536 | | 2013 | 44.698986866057 | | 2012 | 44.690637906399 | | 2011 | 44.682808432344 | | 2010 | 44.674978958288 | | 2009 | 44.492943686508 | | 2008 | 44.310908414727 | | 2007 | 44.128873142947 | | 2006 | 43.94879523968 | | 2005 | 43.766759967899 | | 2004 | 43.584724696118 | | 2003 | 43.402689424338 | | 2002 | 43.220654152557 | | 2001 | 43.038618880777 | | 2000 | 42.856583608996 | | 1999 | 42.674548337215 | | 1998 | 42.492513065435 | | 1997 | 42.312435162168 | | 1996 | 42.130399890387 | | 1995 | 41.948364618607 | | 1994 | 41.766329346826 | | 1993 | 41.584294075045 | | 1992 | 41.836794613322 | | 1991 | 42.114740942277 | | 1990 | 41.854410929946 | | 1989 | 41.764371978312 | | 1988 | 41.750670398716 | | 1987 | 41.574507232477 | | 1986 | 40.664330873574 | | 1985 | 40.276771907847 | | 1984 | 39.247196069604 | | 1983 | 38.947718686997 | | 1982 | 38.714791833859 | | 1981 | 37.857464424827 | | 1980 | 37.068644913778 | | 1979 | 36.606705944528 | | 1978 | 35.968603809039 | | 1977 | 35.16412534988 | | 1976 | 34.347902679637 | | 1975 | 33.705885807121 | | 1974 | 33.04625261798 |
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