| Year | Value | | 2022 | 0.12642714199328 | | 2021 | 0.22996520165664 | | 2020 | 0.33711962027816 | | 2019 | 0.45690590185934 | | 2018 | 0.54052834554913 | | 2017 | 0.62875707851254 | | 2016 | 0.61698292985855 | | 2015 | 0.64004480761908 | | 2014 | 0.69815689769874 | | 2013 | 0.72788642615487 | | 2012 | 0.72247907011618 | | 2011 | 0.62965394501602 | | 2010 | 0.59500842219651 | | 2009 | 0.64057708521801 | | 2008 | 0.64951638719946 | | 2007 | 0.63953916546558 | | 2006 | 0.64423612126478 | | 2005 | 0.64166312018068 | | 2004 | 0.63788527516644 | | 2003 | 0.65120273540403 | | 2002 | 0.67319031416251 | | 2001 | 0.71764423492182 | | 2000 | 0.75904476069067 | | 1999 | 0.84833491205394 | | 1998 | 0.92481779693333 | | 1997 | 0.97297578962446 | | 1996 | 0.99801647352338 | | 1995 | 1.0294019532811 | | 1994 | 1.0844629384864 | | 1993 | 1.1228097964019 | | 1992 | 1.2046109041399 | | 1991 | 1.2979802157964 | | 1990 | 1.3733350537231 | | 1989 | 1.4806834094062 | | 1988 | 1.5729496081448 | | 1987 | 1.590100213729 | | 1986 | 1.5291424922298 | | 1985 | 1.4623375524265 | | 1984 | 1.4406106955847 | | 1983 | 1.5162601535841 | | 1982 | 1.5431398198266 | | 1981 | 1.43481193472 | | 1980 | 1.4118393515301 | | 1979 | 1.4388503972132 | | 1978 | 1.4590658532657 | | 1977 | 1.520295214281 | | 1976 | 1.6383749924651 | | 1975 | 1.7406487152215 | | 1974 | 1.9282358658608 | | 1973 | 2.0705689740151 | | 1972 | 2.1835153020876 | | 1971 | 2.3580005761601 | | 1970 | 2.3687062880591 | | 1969 | 2.368945475402 | | 1968 | 2.3060296939116 | | 1967 | 2.2959036016937 | | 1966 | 2.4240631188515 | | 1965 | 2.2442489043233 | | 1964 | 2.232495185576 | | 1963 | 2.3224218820866 | | 1962 | 1.3130665398254 | | 1961 | 0.19901077425834 |
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