| Year | Value | | 2022 | 0.225898556796 | | 2021 | 0.17640865073423 | | 2020 | 0.13786926624703 | | 2019 | 0.34787496857753 | | 2018 | 0.43351902761305 | | 2017 | 0.28096801830169 | | 2016 | 0.39685182338114 | | 2015 | 0.52728849740779 | | 2014 | 0.62814986143364 | | 2013 | 0.45521862216466 | | 2012 | 0.52571366060041 | | 2011 | 0.76897175858259 | | 2010 | 0.49822508440111 | | 2009 | 0.5146828275358 | | 2008 | 0.75931668185093 | | 2007 | 0.50523403292034 | | 2006 | 0.52519994049878 | | 2005 | 0.21199778411755 | | 2004 | 0.39633143669781 | | 2003 | 0.51832145298565 | | 2002 | 0.57795727681484 | | 2001 | 0.76724177476028 | | 2000 | 0.83618086429777 | | 1999 | 0.71079459306138 | | 1998 | 0.72186501759031 | | 1997 | 0.93771380892015 | | 1996 | 0.9527794218527 | | 1995 | 1.0062008545768 | | 1994 | 1.0061572450175 | | 1993 | 1.0158214374251 | | 1992 | 1.0391613555734 | | 1991 | 0.98978598182153 | | 1990 | 0.98513049421877 | | 1989 | 0.9890932684583 | | 1988 | 0.97918922415019 | | 1987 | 0.98513311242458 | | 1986 | 0.99472386803381 | | 1985 | 0.98456559710882 | | 1984 | 1.2340183114041 | | 1983 | 1.4742188210884 | | 1982 | 1.545468533084 | | 1981 | 1.5602039923988 | | 1980 | 1.5584626781958 | | 1979 | 1.5168748677583 | | 1978 | 1.5191967189167 | | 1977 | 1.5590393860321 | | 1976 | 1.5965585940723 | | 1975 | 1.6820000547482 | | 1974 | 1.712705419969 | | 1973 | 1.7682927120788 | | 1972 | 1.8759993696699 | | 1971 | 1.9713236575205 | | 1970 | 2.1841739468947 | | 1969 | 2.2634340391652 | | 1968 | 2.3203510913178 | | 1967 | 2.3350136933305 | | 1966 | 2.5143874318472 | | 1965 | 2.5421509508381 | | 1964 | 2.6153946351602 | | 1963 | 2.7848200527187 | | 1962 | 2.8593208116045 | | 1961 | 2.9672439729528 |
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