| Year | Value | | 2022 | 1.82337042207 | | 2021 | 0.57542191647036 | | 2020 | 1.0737958268224 | | 2019 | 1.4361368231689 | | 2018 | 1.41245586918 | | 2017 | 1.1995207105787 | | 2016 | 1.1323486546661 | | 2015 | 0.74633947796981 | | 2014 | 1.0053375786738 | | 2013 | 1.0565912591779 | | 2012 | 1.0858172630476 | | 2011 | 0.97869778657034 | | 2010 | 1.1118640751717 | | 2009 | 1.1417580991216 | | 2008 | 1.0829071160701 | | 2007 | 0.97113514136806 | | 2006 | 1.0103345027004 | | 2005 | 0.94446692745073 | | 2004 | 0.93302077749518 | | 2003 | 0.90137273909595 | | 2002 | 1.0874479271867 | | 2001 | 1.0863509656272 | | 2000 | 0.93128155345243 | | 1999 | 0.81284262371617 | | 1998 | 0.82990935332374 | | 1997 | 0.99378859146519 | | 1996 | 1.0453117831183 | | 1995 | 1.0347694838683 | | 1994 | 1.0952581070613 | | 1993 | 1.0989308788788 | | 1992 | 1.1836755413894 | | 1991 | 1.2427612313168 | | 1990 | 1.5076606728481 | | 1989 | 1.7941935149194 | | 1988 | 1.29662488996 | | 1987 | 1.318167781745 | | 1986 | 0.99404015063097 | | 1985 | 0.91377427539001 | | 1984 | 0.94403471604109 | | 1983 | 0.98848756714777 | | 1982 | 1.1896243407757 | | 1981 | 1.2333972548053 | | 1980 | 1.2895949784716 | | 1979 | 0.9896987332347 | | 1978 | 0.99545694441135 | | 1977 | 1.1702568778327 | | 1976 | 1.315806565588 | | 1975 | 1.45942491324 | | 1974 | 1.3960216692737 | | 1973 | 1.2226165842685 | | 1972 | 1.1608465665146 | | 1971 | 2.9481945276144 | | 1970 | 1.3978316003313 | | 1969 | 1.3597834720838 | | 1968 | 1.6134085034638 | | 1967 | 1.7993565048013 | | 1966 | 1.8628137710139 | | 1965 | 1.8101665970088 | | 1964 | 1.8857149433614 | | 1963 | 1.8628459276353 | | 1962 | 1.859888233399 | | 1961 | 1.9991845569003 |
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